water consumption and water demand lecture 1

7/17/2019 Water Consumption and Water Demand Lecture 1

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UNIVERSITY OF STUTTGART

Consumption and Demand

1

Water Demand, Supply andDistribution


Dipl.-Ing. Ralf Minke, AOR

Institute for Sanitary Engineering,

Water Quality and Solid Waste Management (ISWA)

- Chair of Sanitary Engineering and Water Recycling -





2

Copyright

The slides of this file or presentation contain images which are

not quoted or which are quoted insufficiently. This presentation

is just intended for internal use as a learning aid. Principially

there is a copyright on the entire contents. The permission of the

author needs to be obtained before any further publishing.





3

CWSS Overview

5 Elements of Centralized Water Supply Systems:

Collection – Transport – Treatment – Storage - Distribution





4

Definitions

Water In a provided area actually delivered

Consumption: and measured water quantity.

Water Demand: Estimation of the water quantities to be deli-

vered in an area of supply at the end ofdesign period.

Base for the planning and design of a

water supply system.

Water Demand Forecast of the water consumption expected

Calculation: in an exactly defined area of supply within a

certain design period.





5

Example: Forecast and Reality….

Development of water consumption in households and

water demand prognosis

(old federal states of Federal Republic of Germany)

[L / Inh. * d]

Water consumption in households and

small businesses, Germany





6

Water Demand, Supply and DistributionNecessity for water supply?

Water consumption

1) To survive:

drinking water: 3 – 10 [l/C*d]

2) For hygienic reasons:

drinking water, preparing food, wash up dishes,

body care, washing of clothes, cleaning 15 – 25 [l/C*d]

3) For comfort:

2) PLUS Flushing toilets: 40 – 60 [l/C*d]

2) PLUS Flushing toilets, shower, bath: 80 [l/C*d]

2) PLUS 3) PLUS irrigation of gardens,

swimming pools, car washing: 100 – 600 [l/C*d]

4) For activities: agricultural irrigation: 400 – 1,700 [l/C*d]

public and commercial activities: 50 - 200 [l/C*d]

industrial activities: 30 – 1,300 [l/C*d]





7

Water Demand, Supply and DistributionNecessity for water supply?Consumer Groups (Types of Water Demand)

Domestic Demand: Households, Gardens, Small Business

Agricultural Demand: Inhabitants and livestock in farms,

irrigation

Large Buyers Industries and all buyers with individual

Demand: contract

Public Demand: Administration, Schools, Hospitals,

Kindergardens…

Own needs of Water Rinsing of pipes, Filter-Backwashing,Works and Losses: Leakages, Meter inaccuracies

Demand for fire-fighting: Water supply for the fight against fire





8

Influences on Water Consumption

Living standardClimate

Type of Water Supply System & Wastewater disposal

Industrial characteristic of provision

Water tariff – Measuring - Billing

Water Quality

Provision pressure

Environmental awareness

Technical Progress

E l f I fl W t C ti





9

Example for Influence on Water Consumption:

Water Supply System

Type of Water Supply SystemWater Consumption

Range Average value

[-] [l / C * d] [l / C * d]

Communal Water

Point / Village Well

Distance ~1,000 m 5 - 10 7

Distance 500 – 1,000 m 10 - 15 12

Distance ~250 m 15 - 25 20

Communal

Standpipe Distance ~250 m 20 - 50 30

Yard Connection 20 - 80 40

House ConnectionSingle Tap 30 - 60 50

Multiple Tap 70 - 250 150





10

Consumption Characteristics

60

70

80

90

100

110

120

130

140

0 30 60 90 120 150 180 210 240 270 300 330 360

Time [d]

av

eragemonthlywatercon

sumptionin%

ofth

annualmean

Northern Germany

Southern Germany

Monthly fluctuations:

Average monthly water consumption in northern and southern Germany





11


Weekly fluctuations:

Example for weekly water consumption in summer season (Germany)

0

10

20

30

40

50

60

70

80

90

100

110

120

130

140

150

2. Jun 9. Jun 16. Jun 23. Jun 30. Jun 7. Jul 14. Jul 21. Jul 28. Jul 4. Aug 11. Aug 18. Aug 25. Aug

date

av

erageweeklywaterconsum

ption

in%

ofth

annualmean

air-temperaturein°C

water consumption

air temperature





12


Daily fluctuations:

Example for daily water consumption in Stuttgart in 1995

0

100

200

300

400

0 30 60 90 120 150 180 210 240 270 300 330 360

Time [d]

Averagedailywatercon

sumption

[L/C*d]

Wasserverbrauch in Stuttgart 1995

Easter Whitsun Sundays

Monday

Sunday

Water consumption of Stuttgart in 1995





13


Hourly fluctuations:

Typical hourly fluctuations of water consumption for different types of

communities

Qhmax

0

2

4

6

8

10

12

14

16

0 2 4 6 8 10 12 14 16 18 20 22 24

hour of the day

hourlyconsumptionin%

ofdailyconsumption rural village

small town

big town





14

Forecasting Water Demand: Water Demand Calculation

Definition: Forecast of the water consumption expected

in an exactly defined area of supply within a

certain design period.

Task of Forecasting the development of the different

Engineer: consumer groups and their consumptionbehavior on the base of an exact analysis of

actual situation.

Goal: To determine the most correct design peakflows for all parts of a water supply system





15


Advance:

1. Priority: Detailed analysis of existing area of supply

Measuring current state and analysing

development in the past

Forecasting Development

2. Priority: Detailed analysis of the most similar area ofsupply

Measuring current state and analysing

development in the past

Forecasting Development

Check transferability

3. Priority: Use of average values from statistics

(Germany: DVGW W 410)

I n c r e a s e i n un c er t ai n t y / i n a c c ur a

c y





16


In Germany consumption characteristics of households and

small businesses are taken into account as follows:

(acc. to DVGW W 410 Definitions and statistical values)

qdm: average specific daily demand

= yearly demand / 365 days [L/Inh.*d]

qdmax: maximum specific daily demand = qdm * f d [L/Inh.*d]

f d: maximum daily peak factor [-]

f h: maximum hourly peak factor [-]

qhmax: maximum hourly specific demand = f h * qdm / 24 [L/Inh.*h]





1717

Demand Calculation

Demand Values and Peak Factors(DVGW 410)

Small Areas up to 1000 Inhabitants(Housing Areas = Domestic Demand)

Maximum hourly specific demand is relevant

log qhmax = 0.1099 * (log Inh.)² - 0.9729 * (log Inh.) – 0.1624

0,001

0,010

0,100

1,000

1 10 100 1000

E i n w o h

n e r b e z o g e n e r

S p i t z e n b

e d a r f i n L / ( E * s )

Einwohner EInhabitants Inh.

M a x i m u m h

o u r l y s p e c i f i c d e m a n d i n L / I n h . * s

]





1818

Demand Calculation

Inhabitants Housing Units Peak Demand

qhmax Qhmax Qhmax

Inh. HU L/(Inh.*s) L/s m³/h

1 0.688 0.688 2.48

2 1 0.3587 0.717 2.58

4 2 0.1958 0.783 2.82

10 5 0.0943 0.943 3.40

20 10 0.0573 1.145 4.12

100 50 0.0214 2.145 7.72

200 100 0.0152 3.033 10.92

400 200 0.0112 4.490 16.16

1000 500 0.0081 8.091 29.13

Small Areas up to 1000 Inhabitants

qhmax as f(number of inhabitants) * number of inhabitants = Qhmax





1919

Demand Calculation

19

Demand Calculation

Areas > 1000 Inhabitants

(Housing Areas = Domestic Demand)

Calculation of Qdmax and Qhmax using Peak Factors

Qhmax = f h * Qhm = f h * Qa/(365*24)

Qdmax = f d * Qdm

With: f h = 18.1 * Inh.-0.1682

and: f d = 3.9 * Inh.-0.0752

Inhabitants f h f d

1,000 5.66 2.3210,000 3.84 1.95

100,000 2.61 1.64

1,000,000 1.77 1.38

„The bigger the Area, the smaller the Peak Factors“

f d Tagesspitzenfaktor

f h S tundens pitzenfaktor

0,00

1,00

2,00

3,00

4,00

5,00

6,00

1000 10000 100000 1000000

E inwohner E

S

p i t z e n f a k t o r

Maximum hourly peak factor f h

Maximum daily peak factor f d

Inhabitants Inh.

P e a k f a c t o r

Why ????





2020

Demand Calculation

20

Demand Calculation

20

Demand Calculation

Public and Small Businesses Demand (W 410)

Consumer Group Unit Specific Demand

Value (Average)

Specific Demand

Values (Range)

f d f h

Hospitals

Patient and

Employee

0.34 m³/(PE*d) 0.12 – 0.83

1.3 3.2

Bed 0.50 m³/(B*d) 0.13 – 1.2

Schools Pupil/Student and

Teacher

0.006 m³/(PT*d) 1.7 7.5

Administration Employee 0.025 m³/(E*d) 0.013 – 0.111 1.8 5.6

Hotels

Guest 0.29 m³/(G*d) 0.10 – 1.40

1.4 4.4Room 0.39 m³/(R*d) 0.07 – 1.4

Agriculture/Farms Großviehgleichwert 0.052 m³/(GVGW*d) 1.5 7.6

Commercial Areas Area 2 m³/(ha *d) 1.5 – 4.0

1.8 5.6Working Place 0.05 m³/WP*d) 0.025 – 0.125





21


Design periods:

Pumps, Motors, mechanical equipment,additional areas of distribution networks: 5 - 10 a

Wells, buildings, Water treatment facilities,

Water storage tanks: 10 - 15 a

Water Towers, Long distance Pipe-lines,

Distribution networks in settled areas: 15 - 30 a

Dams, storage reservoirs: 30 - 40 a





22


Forecasting development of consumer groups

1. approximation: Pn = P0(1+p/100)n with : n…number of years

p…growth rate in %

But:No development without limit!!

Solution: Use of best fitting Forecast-function as a result

of development in the past and limitations of planning area





23


arithmetic

P o p u

l a t i o

n

Time [years]

declining growth

logistic

exponetiell

Forecast functions:





24


arithmetic

P o p u

l a t i o

n

Time [years]

declining growth

logistic

exponetiell

Arithmetic Growth: Increase of population is const.

P(t) = P0 + K * t with K = dP/dt

Exponential Growth: Growth Rate is constant

P(t) = P0 * eK´*dt with dP/dt = K´*P

Logistic Growth: The curve modelling population growth has a S-Shape

P(t) = Psat/(1 + e a + b*dt)

where Psat is the saturation population in the area; a and b are constants.

a, b and Psat may be determined from at least 3 censuses.

Declining Growth: Growth is a function of population deficitP(t) = P0 + (Psat – P0)(1 – e K´´ * dt) with dP/dt = K´´*(Psat – P(t))





25


Forecasting behaviour of consumer groups

Trend: decreasing specific consumptions in all consumergroups, especially in industry !!

0

10000

20000

30000

40000

50000

1979 1983 1987 1991

UsedquantityandInput[1

06m3/a]

0

1

2

3

4

5

Utilisationfactor[-

]

Input

Used quantity

Utilisation factor

Development of water input and used water quantity in the industries of the old federal

states of the Federal Republic of Germany



UNIVERSITY OF Consumption and Demand

26

Homework

3 Questions at the end of each chapter:

1) What are the reasons for the fact: „the bigger the area,

the smaller the peak factors“?

2) What is your personal qdm in [L/Inh. *d]?

3) Pumps are dimensionend for a design period of 10 years

whereas Water Towers or Long-Distance-Pipelines are

dimensionend for a design period of 30 years. Why?

water consumption and water demand lecture 1

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