Transcript Water Demand Management (WDM)

Water Demand
Management (WDM)
Lecture 5
IWRM
IWRM, Global Water Partnership 2000


A process which promotes the coordinated development
and management of water, land, and related resources in
order to maximize the economic and social welfare in an
equitable manner without compromising the sustainability
Four Dimensions:
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1.
Resources
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2.
3.
Water users
Spatial Scale
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4.
Quantity
Quality
Jurisdiction level
System boundaries
Temporal Scales and patterns
Water Demand Management (WDM)
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Water Demand management aims at achieving desirable demands
and desirable uses. It influences demand in order to use a scarce
resource efficiently and sustainably.
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WDM is not necessarily the same as decreasing water demand; in
certain situations managing the demand may mean to stimulate
the demand that had been suppressed, here we have to improve
water services and increase water consumption
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WDM uses technical, legal and economic incentives in
combination with awareness raising and education; in order to
achieve more desirable consumption patterns, both in terms of
distribution between sectors and quantities consumed, coupled
with an increased reliability of supply.
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WDM is always concerned with increasing the efficient use of
water. Minimizing leakages is often the most cost-effective
strategy towards system's improvement.
Water Demand Management
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Goals of demand-side management of water
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Increased efficiency of water use
Safeguard the right of access to water for future
generations
Improve allocation among competing users
Decreased need for large investments in
infrastructure (like dams, Desalination Plants)
More cost effective water use
Changes to the nature of water demand and the
way people use water
WDM Tools / Instruments
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Technical / regulatory tools
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Reduction of water losses
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Improved O&M
Metering
Rationing
Cropping patterns
Timing and regulations of outdoor irrigation
Dual distribution system
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Good quality for drinking and cooking
Lower quality for other uses
Internal recycling
Water savings appliances/devices
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Leak detection and repair
Inspection of illegal connections
Modern irrigation techniques
More crop for drop
Automatic taps
Spray showers
Dual flush system
Rainwater harvesting / promote reclaimed WW (supply side)
WDM Tools / Instruments
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Social tools
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Economic tools
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Behavioral changes
Public awareness
Education curricula
Water pricing
 Increasing block tariff
Implementation incentives
 Subsidies
 Taxes
 Loans
 Promotions for compliance
 Fines / penalties / fees
Legal tools
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Policies / laws
Regulatory framework
Global Water Resources
Global Water Resources
River Basin Water Balance
S
 P  ET A  Q
t
Water Demand – Municipal &Industrial (M&I)
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Factors:
 Population and population density
 Housing type and standard of living
 Sanitation type
 Climate conditions
 Economic conditions and income level
 Water availability – Rationing
 Water quality
 Pricing policies and tariff structure
Per - Capita Demand
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Basic Human Needs
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WHO (guidelines for small communities)
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Average 150 l/c/d
Minimum 100 l/c/d
Per - Capita Demand
150 l/c/d
300 l/c/d
420 l/c/d
165 l/c/d
Per - Capita Demand
‫االحتياجات الفردية‬
‫‪‬‬
‫المنزلي ( االستعمال داخل المنزل‬
‫‪‬‬
‫‪‬‬
‫)‪1‬‬
‫الحد االدنى = ‪ 100‬لتر للفرد في اليوم‬
‫المتوسط = ‪ 150‬لتر للفرد في اليوم‬
‫‪ ‬الخدمات العامة ( يشمل متطلبات المساحات الخضراء و الدفاع المدني )‬
‫‪ ‬تقدر بحوالي ‪ %5‬من االجمالي‬
‫‪‬‬
‫الصناعي‬
‫‪‬‬
‫من ‪ %7‬حاليا الى ‪ %14‬في ‪2020‬‬
‫* أقل من ‪ %15‬من مصادر مياه الشرب تعتبر مطابقة للمواصفات المحلية‬
‫‪1- WHO guidelines for water supply systems‬‬
‫‪in small communities‬‬
‫اإلحتياجات اإلجمالية‬
*
* Based on PCBS including the returnees before 2000
Population
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Growth rate:
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dp
 B  D  I O
dt
dP/dt = change in population during time step (capita)
B = number of birth per unit of time (capita/year):
P
Bb
L
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b is the birth rate which the amount of
children born per person during his/her life
D = number of death per unit of time (capita/year)
P
Dd
L
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Similar to
Water Balance
d is the death rate
d = 1 : steady state situation
I = immigration (capita/year)
d < 1 : population is growing where more
O = emigration (capita/year)
young people than old people.
L= life expectancy (year)
d > 1 : more elder people than young
people ( case of china b=0.5) where b < 1.
Population
Ignoring immigration and emigration
dp b  d 

P  r.P
dt
L
P  P0 .e
1- if (b-d)> 0: more children are born than die
2- b=d: the population is constant.
r .t
The exponential growth model can also be written as:
P  P0 (1  r ) t
Other models: Linear Model:
P  Const.
Population
P  P0 .e r .t
3000
r=0.033
2500
Number of children 4
2000
r=(4-2)/60=0.033
Number of children 5
r=(5-2)/60=0.05
population
Example:
r=0.05
1500
1000
500
0
1
3
5
7
9
11 13
years
15
17
19
Population
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Other models: Saturation model
Ps
P
t
Gaza Population
2,300,000
2,200,000
1377500
1,400,000
1,300,000
ACTUAL POPULATION
(PALESTINIAN DATA)
800,000
700,000
600,000
1022207
1,000,000
900,000
1110000
1,200,000
1,100,000
ACTUAL POPULATION
(ISRAELI DATA)
1597000
1,700,000
1,600,000
1,500,000
1851000
WSSPS estimation
(50,000 returnees,
decreasing population
growth rate from 3.5%
to 3.1% )
1,900,000
1,800,000
500,000
400,000
300,000
200,000
YEAR
2020
2018
2016
2014
2012
2010
2008
2006
2004
2002
2000
1998
1996
1994
1992
1990
1988
1986
1984
1982
1980
1978
1976
1974
1972
1970
100,000
0
1968
POPULATION
2146000
2,100,000
2,000,000
Population Pyramid
Irrigation Water Demand
ETo: Reference evapotranspiration: The evapotranspiration rate
from a reference surface, not short of water. The reference surface
is a hypothetical grass reference crop with specific characteristics
Single Crop Coefficient - Kc
Case A: Pan placed in short green cropped area
RH mean
(%)
low
< 40
Wind
speed
(m s-1)
Medium
40 - 70
Case B: Pan placed in dry fallow area
High
> 70
Windward side
distance of
Green crop (m)
low
< 40
medium
40 - 70
high
> 70
Windward side
distance of dry
fallow (m)
Light
1
.55
.65
.75
1
.7
.8
.85
<2
10
.65
.75
.85
10
.6
.7
.8
100
.7
.8
.85
100
.55
.65
.75
1000
.75
.85
.85
1000
.5
.6
.7
Moderate
1
.5
.6
.65
1
.65
.75.
.8
2-5
10
.6
.7
.75
10
.55
.65
.7
100
.65
.75
.8
100
.5
.6
.65
1000
.7
.8
.8
1000
.45
.55
.6.
Strong
1
.45
.5
.6
1
.6
.65
.7
5-8
10
.55
.6
.65
10
.5
.55
.65
100
.6
.65
.7
100
.45
.5
.6
1000
.65
.7
.75
1000
.4
.45
.55
1
.4
.45
.5
1
.5
.6
.65
10
.45
.55
.6
10
.45
.5
.55
100
.5
.6
.65
100
.4
.45
.5
1000
.55
.6
.65
1000
.35
.4
.45
Very strong
>8
Factors Influencing Kc
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Crop height: The crop height influences the aerodynamic resistance
term (ra) of the FAO Penman-Monteith equation and the turbulent
transfer of vapour from the crop into the atmosphere.
Albedo (reflectance) of the crop-soil surface. The albedo is affected
by the fraction of ground covered by vegetation and by the soil
surface wetness. The albedo of the crop-soil surface influences the
net radiation of the surface, Rn ,which is the primary source of the
energy exchange for the evaporation process
Canopy resistance: The resistance of crop to vapour transfer is
affected by leaf area (number of stomata), leaf age and condition,
and the degree of stomatal control. The canopy resistance
influences the surface resistance, rs
Evaporation from soil, especially exposed soil.
Initial stage
Crop development stage
Mid-season stage
Late season stage
Estimation of ET0
Penman-Monteith Method
http://www.fao.org/docrep/X0490E/x0490e01.htm
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ETo reference evapotranspiration [mm day-1],
Rn net radiation at the crop surface [MJ m-2 day-1],
G soil heat flux density [MJ m-2 day-1],
T mean daily air temperature at 2 m height [°C],
u2 wind speed at 2 m height [m s-1],
es saturation vapour pressure [kPa],
ea actual vapour pressure [kPa],
es - ea saturation vapour pressure deficit [kPa],
D slope vapour pressure curve [kPa °C-1],
γ psychrometric constant [kPa °C-1].
Tedious Calculations
G ???
Rn ???
Epan Method
ETo = Kp Epan
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ETo reference evapotranspiration [mm/day]
Kp pan coefficient [-]
Epan pan evaporation [mm/day].
Effective Rainfall
(USDAS-SCS Method)

Peff  f  1.25P
0.834
f

 2.93 10
0.000955ET0 
= correction factor depends on average net application depth
or soil moisture depletion before each irrigation
P = the gross monthly rainfall in mm
ET0 = the monthly reference evapotranspiration
CWR  ET0  Kc  Peff
Gaza Example
Gaza Example
Gaza Example
Crop Category
Crop Type
Citrus
Orange / lemon / grapefruit
Fruit trees
Apples / pears / peaches / apricots / almonds
Vegetables1
Cucumber / squash / cabbage
Vegetables2
Tomato / sweet peppers / egg plants / potato
Field crops
Wheat / barley
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Citrus
0.7
0.7
0.7
0.7
0.7
0.7
0.7
0.65
0.65
0.65
0.65
0.65
Fruit trees
0.9
0.9
0.9
0.65
0.65
0.65
0.65
0.4
0.4
0.4
0.4
0.9
Vegetables1
1.15
1.15
0.95
0.6
1
1
0.75
Vegetables2
0.8
0.6
1.15
1.15
0.8
Field crops
1.15
0.3
0.3
1.15
0.6
0.4
0.6
1.15
1.15
0.8
Gaza Example
Gaza Example
Gaza Example
Gaza Example
Gaza Example
Demand-Resources Gap
Other Water Demands
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Environmental Demand
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Environmental flow: the quantity and quality of water
required to sustain aquatic ecosystems and the ecological
components, processes and functions on which people
depend
Ecological functions of flow
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Extreme low (drought) flows
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Low (base) flows
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Provide habitat for aquatic biota, maintain water temperature and
water chemistry, provide drinking water for terrestrial animals
High flows
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Population regulation; life history cues
Shape river channel, prevent encroachment of riparian vegetation,
flush sediments and pollutants, maintain estuaries and floodplain
Hydropower
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Power generation requirements
E = P T = e t eg ρ g Q H T
Water Pricing
Dublin and Rio conferences, Agenda 21: Water should be
managed as an economic good, provided water for drinking
purposes and other basic needs are made available at prices that
are widely affordable locally
Cost of Water

Water pricing should have two purposes:
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to recover costs
to enhance water use efficiency
External costs (economic externalities): environmental damage,
pollution, effect on downstream users and health hazards
The economic price should also reflect the scarcity of the
resource, which is generally expressed in the opportunity cost (the
cost of not being able to use the resource for another social or
economic activity).
Price vs. Demand
Q  cP
E
Q
where
 Q is the quantity of
demand for the good
 P is the price of the good
 c is a constant
 E is the elasticity of
demand (-1 . 0)


Price
Type of use
P
Assumptions:
• constant incomes
• constant preferences
Price vs. Demand
300
Elastic
Rigid
250
Q (l/c/d)
200
150
100
50
0
0
0.2
0.4
0.6
0.8
Price ($/m3)
1
1.2
1.4
Price vs. Demand
450
low income
400
high income
350
Q (l/c/d)
300
250
200
150
100
50
0
0
0.2
0.4
0.6
0.8
Price ($/m3)
1
1.2
1.4
Elasticity of Demand
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If E<=-1, the response to a
price increase is said to be
elastic or reactive.
If -1<<E, the response to a
price increase is said to be
inelastic or rigid.
Essential needs
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More rigid
No alternatives
industry and agriculture
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More elastic
Alternatives available
Elasticity of Demand
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Example:
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What is E if the a price increase by 100% (P1=2*P0) resulted in a
20% decrease in water use (Q1=0.8Q0)?

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dP/P = (P1-P0)/P0 = (2P0-P0)/P0 = 1
dQ/Q = (Q1-Q0)/Q0 = (0.8Q0 -Q0)/Q0 = -0.20
E = -0.20/1= -0.20
Concluding:
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the elasticity of water consumption is generally low.
the price elasticity is greater when the price is higher.
in the household sector, the price elasticity varies between -0.15
and -0.70.
with respect to drinking water the demand-price relation will never
be elastic (E < -1)
in the industrial sector, the majority of estimates are in the range of
-0.45 to -1.37.
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Example:

Does increasing price result
in increasing revenues?

E
Revenues = QP
rigid

(1+E)>0 ???
elastic
Increasing Block Tariff

Considerations


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Cost recovery
Equity (access to
basic needs)
Block purpose:
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Cross-subsidy
from rich to poor
users
Compromise
between full cost
recovery and
equity
Increasing Block Tariff Example
Block 1:
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
the poorest households have access to a lifeline amount of water and do not
spend more than a certain percentage of their income on water
subsidized
Block2:




ideal’ per capita water consumption level
ensure “well-being” e.g. twice the lifeline amount
charged at the full cost of water supply for the amount above block1
some subsidy
Block 3:


above the well-being amount but less than a certain upper limit (e.g. 4 times
the lifeline amount)
Charged at full cost of water over their entire use
Block 4:

water use above the amount specified in the third block will be charged at a
rate that will off-set the subsidy received by households falling within blocks
1 and 2
Increasing Block Tariff Example
Increasing Block Tariff
South Africa Example
Introduction to
Economics of Water
Resources
Some Economic Indicators

NPV

Internal Rate of Return (IRR)
Interest Rate where NPVcost=NPV benefits

Economic Efficiency
Marginal Cost = Marginal Benefits
Economic Efficiency
TC
P
TB
MC
max
AC
MB
Q*
Quantity