Population Growth And Forecast And Water Demand Part 2

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Introduction And Population Growth And Forecast And Water Demand Part 2

Introduction And Population Growth And Forecast And Water Demand Part 2

Introduction And Population Growth And Forecast And Water Demand Part 2.

In the intricate web of global challenges, few issues carry the weight and urgency of population growth and its ramifications on essential resources like water. As our world population continues its upward trajectory, the demand for water escalates in tandem, straining already stressed ecosystems and pushing the limits of sustainable resource management.

Within this context, understanding the intricate relationship between population dynamics and water demand becomes not only crucial but imperative for devising effective strategies to navigate the challenges ahead. This blog post delves into the intricate interplay between population growth, forecasting, and its profound implications on water demand, unraveling the complexities that lie at the intersection of human demographics and natural resource management.

Embarking on this exploration necessitates a multi-faceted approach, considering demographic trends, technological advancements, socio-economic factors, and environmental sustainability. Through insightful analysis and informed projections, we aim to shed light on the evolving landscape of global population dynamics and its profound implications on water resources.

Join us on this journey as we dissect the complexities, unravel the uncertainties, and illuminate pathways towards a more sustainable future in the face of burgeoning population growth and escalating water demand.

factor affecting per capita water demand

Size of the city:

  • Demand increases with the size of the city.
  • On an average, the per capita demand for Indian towns may vary with the population as shown below:
PopulationPer Capita Demand (lpcd)
20 - 50 Thousand110 - 150
50 - 200 Thousand150 - 240
2 lakhs - 5 lakhs240 - 275
5 lakhs - 10 lakhs275 - 335
>10 lakhs335 - 360
Table 1 Per Capital Demand

  • The above figures are liable to variation up to about 25%, for Indian condition IS Code permits a maximum value of 335 lpcd.

Climate condition:

If the community is located in a hot climate water use will be increased.

Standard of living:

The higher the standard of living is, the high water the demand.

Quality of water:

Poor quality of water results in a reduction in use.

Pressure in the supply:

High pressure results in increased use while low-pressure results in decreased use.

System of supply:

Water supply may either be continuous or intermittent. Generally, intermittent supply will reduce the rate of demand.

Water rates:

An increase in water rates will reduce consumption in the metred areas.

Example 3: Which of the following factors increases the water demand of a community?

I. Hot climatic condition
II. High cost
Ill. Intermittent sewerage system
IV. Extension of industrialisation
V. Good quality of water
VI. Metering
VII. Pressure

(A) I, IV, V, VIII
(C) I, II, V, VII
(D) 1, IV

Solution: (D)

Water demand increases with:

  • Size of city
  • Flushing sewerage system
  • extent of industrialisation
  • Good way of living
  • Hot climatic condition

Water demand decrease with:

  • Intermittent sewerage system
  • Cold climatic condition

Water consumption increases with:

  • Quality of water
  • Pressure in the distribution system

Water consumption decreases with:

  • Cost of water
  • Policy of metering

Water demand

  1. Whenever an engineer is given the duty to design a water supply scheme for a particular section of the community.
  1. The first requirement is to calculate the demand and then the second requirement is to find sources to fulfil the demand.
  2. Introduction And Population Growth And Forecast And Water Demand Part 2.

Various types of water demands are:

  1. Domestic water demand:

a) This includes the water required in the private building for drinking, cooking, bathing, gardening purpose, etc., which may vary accordingly to the living conditions of the consumers.

b) The total domestic water consumption usually accounts for 50-60% of the total water consumption.

c) IS code recommended, domestic water consumption limit between 135-225 Ipcd.

d) Under ordinary conditions the minimum domestic water demand for a town with a full flushing system should be taken as 200 l/h/d although it can be reduced to 135 l/h/d for economically weaker sections and LIG 9Low Income Group) colonies depending upon prevailing conditions.

e) The breakup of 200 /h/d and 135 l/h/d are given in table 2.

Consumption in Litres Per Head Per Day (l/h/d)
S.NOUseCities with full flushing SystemsWeaker Section and LIG colonies in small town and cities
4.Washing of Clothes2520
5.Washing of Utensils1510
6.Washing and Cleaning of houses and residences1510
7.Lawn watering and gardening15-
8.Flushing of water closet, etc.4530
Table 2. Minimum Domestic Water Consumption of Indian Towns and Cities.

Introduction And Population Growth And Forecast And Water Demand Part 2.

2) Institutional and commercial water demand:

a) On average, a per capita demand of 20 l/h/d is usually considered to meet such commercial and institutional water requirements.

b) This demand is as high as 50 l/h/d for highly commercialised cities.

c) The individual requirement would be as follows:

1.School/Colleges45 - 135 lpcd
2.offices45 lpcd
3.Restaurants70 (per seat)
4.Cinema and Theatre15 lpcd
5.Hotels180 lit./bed
6.Hospitals340 lit./bed (when beds are < 100)
450 lit./bed (beds > 100)
Table 3. Water Demand for various institutions

3) Industrial Water Demand:

a) In Industries cities, the per capita water requirement may finally be computed to be as high as 450 l/h/d as compared to the normal industrial requirement of 50 l/h/d.

b) Water Demand of certain important industries (As per GOl Manual).

Name of IndustryUnits of ProductionApproximate Quantity of Water
( in kilolitres Required Per Unit of Production)
FertilizersTon80 - 200
LeatherTon (or 100kg)40 (or 4)
PaperTon200 - 400
Petroleum RefineryTon (crude)1 - 2
SugarTon (cane Crushed)1 - 2
Table 4 Industrial Water Demand

4) Fire Demand:

a) For a total amount of water consumption for a city of 50 lakhs population hardly amounts to 1 lpcd for fire demand.

b) Following requirements must be met for the fire demand:

For cities housing population exceeding 50,000, the water required in kilo-litres may be computed as:
Fire demand = 100√P
Where P = Population in Thousands.

Fire Demand


For towns where buildings of one-storey is common, the minimum residual pressure at ferrule point should be 7 m for direct supply to the ground level storage tanks, and where two or three storeyed buildings are common residual pressure should be 12 m or 17 m.

1. Kuchling Formula

Fire Demand, Q = 3182√P (l/min).
Where, P = Population in thousands.
Q = Amount of water required in litres/

2. National Board of fire Under Writers Formula

a) For a central congested high valued city when the population is " 2 lakhs.
Q = 4637√P{ 1- 0.1√P } l/min
Where P is in thousands.
C = Amount of water required in

b) When the population is > 2 lakhs, a provision for 54600 l/min may be made with an extra additional provision of 9100-36400 l/min for a second fire.

3. Freeman formula

Q = 1136{(P/10) + 10}
Where P is in thousands.
Q = Amount of water required in litres/

4. Buston's Formula

Q = 5,663√P

Water demand for losses and theft:

  1. This includes the water lost in leakage due to bad plumbing, stolen water due to unauthorised water connection, and other losses and wastes.
  2. This amount may be as high as 15% of the total. Per capita demand:

Per Capita demand:

1. This is the annual average amount of daily water required by one person and includes the domestic use: wastes, theft, etc.

2. Per capita Demand (q) in litres per day per head = Total yearly water requirement of the city in litres/(365 x Design of population).

variation in demand and thier effects:

  1. The smaller the town, the more variation in demand. The shorter the period of the draft, the greater the departure from the mean.
  2. The maximum demands (monthly, daily or hourly) are generally expressed as ratios of their means.

Maximum daily consumption:

= 1.8 x Avg. Daily Consumption = 1.8 q

Maximum hourly consumption:

Maximum hourly consumption of maximum day, i.e., peak demand
= 1.5 x Avg. hourly consumption of maximum day

= 1.5 x 1.8 x q/24

= 2.7 q/24

= 2.7 Avg. Daily Demand.

Maximum weekly demand:

= 1.48 x Avg. Weekly Demand

Maximum monthly demand:

= 1.28 x Avg. Monthly Demand

Good-rich formula to find peak demand t an overage demand ratio:

P = 180 x t-0.1
where, P = percent of the annual overall draft for the time 't' in days.

Peak factor:

1. The fluctuation in consumption is accounted for any considering the peak rate of consumption which is equal to the average rate multiplied by a peak factor.


The following peak factors are recommended for various populations are:
a) Up to 50,000 - 3
b) 50,001 to 2, 00,000 - 2.5
c) Above 2 lakhs - 2
d) For small water supply schemes - 3

Note: As for as the design of the distribution system is concerned, it is the hourly variation in consumption that matters.

Coincident draft:

  1. For general community purpose, the total draft is not taken as the sum of maximum hourly demand and fire demand.
  2. It is taken as sum of maximum daily demand and fire demand or the maximum hourly demand, whichever is more.
  3. The maximum daily demand (i.e., 1.8 x average daily demand) when added to the fire demand is known as the coincident draft.

Design capacity of various components of water supply scheme:

The following recommendations may be adopted for designing the capacities of different components, of a water supply scheme.

  1. Sources of supply may be designed for maximum daily consumption or sometimes for average daily consumption.
  2. The pipe mains (to take water from sources to service reservoir), filter and other treatment units are designed for maximum daily draft.
  3. The pumps are designed for maximum daily draft plus some additional reserve for break down and repair.
  4. The distribution system (to carry water from service reservoir to water taps) should be designed for maximum hourly draft of maximum day or coincident draft with fire whichever is more.

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