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Greenhouse-gas emissions from energy use in the water sector

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Water management faces great challenges over the coming decades. Pressures include stricter water-quality standards, increasing demand for water and the need to adapt to climate change, while reducing emissions of greenhouse gases. The processes of abstraction, conveyance and treatment of fresh water and wastewater all demand energy. Energy use in the water sector is growing, yet its importance is under-recognized, and gaps remain in our knowledge. Here we define the need to integrate energy use further into water resource management and identify opportunities for the water sector to understand and describe more effectively its role in greenhouse-gas emissions.
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C
limate change represents a huge challenge to the sustainable
management of water resources. In recent decades, develop-
ments in industrial, agricultural and domestic water use, and
in water-quality regulation, have greatly intensied the treatment
and transport of water
1
. Moreover, rising demand for food and bio-
fuels, and their international trade, threaten to drive expansion of
irrigated cropland and cropping intensity and hence greater use of
water for agriculture. ese activities generally require high energy
consumption and have contributed to increases in energy use in the
water sector in many parts of the world
2–4
.
In the United States, the relationship between water and energy,
particularly the use of water for energy generation, is receiving
greater attention because of recent supply issues (for example,
refs1–5). In the United Kingdom, where roughly 3% of generated
electricity is used by the water industry alone, energy eciency is
also of growing interest
6–9
. Some recent studies have highlighted the
importance of greenhouse-gas (GHG) emissions from energy use in
the water sector. ey show that water-related energy use in the US
accounts for nearly 5% of total GHG emissions, and the proportion
is even higher in the UK, although there it is mostly associated with
end uses of water, such as heating
8,10
. In countries with very high
freshwater withdrawals, most of the water is used for irrigation, and
the energy used in its abstraction and conveyance is oen consider-
able
11,12
. Estimates for India suggest that emissions from liing water
for irrigation could be as much as 6% of total national emissions
11
.
In the US, agriculture is the largest business consumer of both elec-
tricity and water, using most of the direct energy to pump ground-
water at an annual cost of almost US$1.2 billion (ref.12).
Adapting water management to meet increasing demand, regula-
tory standards and the eects of climate change will in many cases
require greater energy use. Although there are new government
regulations to monitor the water sector’s GHG emissions in the UK,
and concern about the issue is growing elsewhere (for example, in
South Asia
11,13–15
), there is a gap between water and energy man-
agement in both research and policy. We argue that the energy use
and GHG emissions associated with water management are poorly
understood and have only partially been considered in water man-
agement and planning.
Here we address this issue through a systematic review of
energy use in the water sector, based on searches in ISI Web of
Greenhouse-gas emissions from energy use in the
water sector
Sabrina G.S.A. Rothausen
1,2*
and Declan Conway
1,3,4*
Water management faces great challenges over the coming decades. Pressures include stricter water-quality standards,
increasing demand for water and the need to adapt to climate change, while reducing emissions of greenhouse gases. The pro-
cesses of abstraction, conveyance and treatment of fresh water and wastewater all demand energy. Energy use in the water sec-
tor is growing, yet its importance is under-recognized, and gaps remain in our knowledge. Here we define the need to integrate
energy use further into water resource management and identify opportunities for the water sector to understand and describe
more eectively its role in greenhouse-gasemissions.
Knowledge and Google Scholar databases with dierent string
terms to obtain suitable literature (see Supplementary Information
and Supplementary TableS1 for more details). We explain the need
for clear denitions of water-sector boundaries and greater stand-
ardization of approaches to proling energy use. We characterize
the full spectrum of energy use in the water sector and dene the
extent of current knowledge on emissions, including those from
agricultural water use. We conclude by outlining opportunities
to aid integration of water resource management and ecient
energy use through regulatory and behavioural responses to meet
futurechallenges.
The water–energy nexus
Dening water-sector boundaries. Water and energy are inextri-
cably linked within what is oen referred to as the water–energy
nexus. e term captures all aspects of water and energy interac-
tions, both within ‘water for energy’ and ‘energy for water’. Water is
an essential component in energy production (cooling, hydroelec-
tric power, some fossil fuel extraction and, increasingly, biofuels),
and energy is used in numerous processes for supplying, treating
and using water. Here our main focus is on ‘energy for water’ and
we consider all aspects of water use in society for which energy
isrequired.
Energy use in the water sector can be split into construction
and operation. ‘Construction’ means infrastructure construction
(for example, wells, conveyance pipes, treatment plants) and manu-
facturing of equipment. ‘Operational’ processes are illustrated in
Fig.1.e energy for maintaining the infrastructure and equipment
in water systems is not shown, but could be added to each step. is
conceptualization is not an exhaustive list of processes; depending
on specic situations, steps may be skipped or repeated, and certain
elements added or excluded.
Some of the links to energy in the water sector are oen over-
looked, and confusion about results may arise through dier-
ences in the scope, methods of assessment and the denition of
boundaries
16
. In particular, end-use processes (Fig.1) are generally
excluded because they occur outside the water industry (for exam-
ple, residential heating of water). Our systematic review reveals that
energy use in the water industry is oen considered within life-cycle
assessments (LCAs). A review of LCAs of the water industry found
1
School of International Development,
2
UEA Water Security Research Centre,
3
Tyndall Centre for Climate Change Research, University of East Anglia, Norwich
NR4 7TJ, UK,
4
Australian National Climate Change Adaptation Research Facility, Visiting Fellow. *e-mail: s.rothausen@uea.ac.uk; d.conway@uea.ac.uk
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that energy use carries the highest environmental burden — in most
cases consumed as electricity for pumping
17
. Some estimates of
construction costs and related GHG emissions in the water industry
are available
18
. Despite being a comprehensive approach, the ele-
ments and processes included in LCA studies may vary, and they
tend to focus on the dierences between water supply systems and
wastewater treatment technologies rather than on the total GHG
emissions of the entire water sector
17
. Furthermore, few studies
consider the trade-os between water and energy in assessing the
carbon footprint of the water sector.
e lack of studies assessing energy use and related GHG emis-
sions in the whole water sector may be partly due to the absence of
clearly dened boundaries. Direct and indirect emissions of GHGs
other than CO
2
, such as CH
4
and N
2
O, which are not strongly asso-
ciated with energy use, are also important in the water sector (for
example, from sludge treatment or chemical production) and essen-
tial for total GHG assessments
16
. Here, however, we focus on CO
2
emissions from energy use. It is important to recognize that energy
may be used from the point of water abstraction to the point where
the water returns to the natural system. Energy assessments need to
view the water sector as a complete system of operational processes
and clearly dene their scope.
An under-recognized issue. Although many studies have inves-
tigated the impacts of climate change on water availability and
demand (for example, ref.19), very few have looked at the impli-
cations of changing water use for fossil fuel use and CO
2
emis-
sions. Studies linking water and energy tend to focus on the use of
water for power generation
1,5,20,21
. However, the water sector is very
energy intensive and also highly sensitive to climate change. e
energy implications of adaptation have not featured prominently in
the Intergovernmental Panel on Climate Change (IPCC) chapters
on hydrology and/or water resources, from the rst to the fourth
assessment reports (see Supplementary Information for references).
Water-related energy is mentioned only in passing and mainly in
relation to hydropower generation or sustainability issues. A recent
IPCC technical report noted that some adaptation options, such
as desalination and pumping, may be inconsistent with mitigation
measures, because they involve high energy consumption
22
. e lat-
est IPCC Working Group III report on mitigation
23
only includes
GHG emissions from wastewater, with no mention of energy use
and eciency in the water sector. In contrast, energy use and emis-
sions in the agriculture sector have received much greater attention
(for example, ref.24).
e low recognition of the relationship between water and
energy use is reected in the lack of peer-reviewed publications
on the subject. Our review shows the literature is dominated by
government agency, private sector and non-governmental organi-
zation reports (‘grey literature’). In some instances, data and
information may be commercially sensitive and restricted from the
public domain. Most of the publications found through our search
concern the use of alternative energy sources for water-treatment
functions or hydropower generation. at so few peer-reviewed
papers address energy use and related GHG emissions in the whole
water sector suggests that a knowledge gap exists in the academic
research community.
In California, recent supply problems with both water and
energy have revealed a lack of understanding of their close relation-
ship and focused attention on enhancing energy and water secu-
rity by exploring the connections between the two resources
2,25
. A
report by the US Department of Energy to Congress highlights this
interdependency and presents the lack of integrated planning as
an important issue for the growing energy insecurity
3
. A review of
productivity and eciency in the water industry also identies a
separation between environmental management, policy and regu-
lation, commercial water supply and wastewater processes, arguing
that the limited research on the interface between these areas may
lead to ineciencies in water-sector processes
26
. Environmental
targets and water-supply strategies tend to be poorly integrated
with energy eciency and climate change policies
7
. Cooperation
between water and energy professionals must be strengthened to
avoid inecient use of water and/or energy, and prevent adverse
environmental consequences
27
. However, the situation is changing,
particularly in response to government regulation of GHG emis-
sions from the water industry. For example, the US and UK are
producing more comprehensive assessments of energy use and
related GHG emissions, although most of these lie outside the
peer-reviewed literature.
Energy use in the water sector
Assessments of energy use. As mentioned above, in the UK the
water industry uses around 3% of total national electricity consump-
tion. Its energy use has increased substantially over the past 20years,
with power costs making up 13% of total production costs and only
10% of power originating from renewable sources
7,28
. Wastewater
collection and treatment have caused the biggest increase as a result
of higher standards for water quality and environmental regula-
tion
29
. About 4% of electricity consumption in the US is used for
transport and treatment of water
4
, and in certain states the propor-
tion is higher.
We compiled studies of energy use and GHG emissions in the
water sector to show the energy or GHG emission intensity of dier-
ent water-related processes (Table1). It is clear that water/wastewater
treatment encompass highly energy-intensive processes. In addi-
tion, some studies note how limited accessibility of water resources
can greatly increase energy use for supply, conveyance and, in cases
where desalination is used, for treatment of water. ese studies
focus on dierent aspects of the water sector depending on their
Figure 1 | A conceptual model of water-sector processes involving energy use.
Pumping of groundwater,
surface water and
salt water
Transfer of water
from source
to treatment plant
or reservoir
Filtration
Oxidation
Ultraviolet treatment
Additives
Denitrification
Desalination
Pumping
Heating
Cooling
Household appliances
Commercial appliances
Industrial processes
Collection
Physical treatment
Chemical treatment
Sludge treatment
Discharge
Abstraction
and
conveyance
Treatment
and
distribution
Wastewater
treatment
End use
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level of detail and the boundaries used for the assessment. ey
tend to focus on certain processes, for example, indirect energy use
for administration of water treatment plants and for production
of chemicals or water bottles. Most importantly, few of the studies
include end use of water. e concept of end use was rst presented
and quantied by Cohen etal.
30
and Klein etal.
31
, who highlighted
its importance in residential and commercial/industrial contexts.
Previously this key component had generally been unaccounted for,
and this continues to be the case: LCA studies oen fail to include
end use because it occurs outside the water industry. Yet end-use
processes oen have the highest energy intensity of all water-sector
elements and deserve far greater attention.
e River Network, a US-based non-governmental organiza-
tion, recently published a report compiling estimates of the US
carbon footprint of water-related energy use, which shows a total
annual emission of 290 million tonnes CO
2
equivalent (CO
2
e), of
which 205 million tonnes is associated with end use
10
. is gure
is almost 5% of total GHG emissions in the US. e estimates of
the River Network are much higher than those of energy use in
the water sector published by the Electric Power Research Institute
(EPRI)
4
, which amounted to 123,000 GWh (~70 Mt CO
2
e). e
EPRI estimate, however, has been criticized for not consider-
ing all processes in the water sector (end use, in particular) and
thereby signicantly underestimating water-related energy use
10
.
Furthermore, the EPRI focused on energy security for water sup-
ply and only included electricity use while excluding other energy
sources. Figure2 shows the distribution of carbon emissions from
energy use in the US water sector, which again highlights end use
(in this case, heating of water) as both the most energy-intensive
and highest GHG-emitting process
10
.
In the UK, a similar estimate by the Department for Environment,
Food and Rural Aairs (Defra)
8
found that the water sector emits
around 41 million tonnes CO
2
e per year (Fig.3). End use also seems
to be very important in this case, comprising 70–90% of potable
water-related energy use. Domestic water heating accounts for 5.5%
of UK total GHG emissions, whereas the rest of the potable water
sector accounts for 0.8%, with wastewater treatment being the dom-
inant process. is study does not include energy use for directly
abstracted water in agriculture and the industrial sectors, which use
35.5% more water than the potable water sector (see Fig.3). In both
the River Netwerk and Defra studies, heating of water (part of end
use) stands out as the most signicant water-related energy use.
Table 1 | A selection of studies on energy use and GHG emissions in the water sector.
Author and region Method Water-sector processes Estimated energy or GHG intensity Unit
Friedrich et al.
61
South Africa
LCA of carbon footprint of
water supply and sanitation
Abstraction
Treatment
Distribution
Collection
Wastewater treatment
Bottled water
51
219
139
150
112
0.9–703
kg CO
2
Ml
–1
kg CO
2
Ml
–1
kg CO
2
Ml
–1
kg CO
2
Ml
–1
kg CO
2
Ml
–1
kg CO
2
Ml
–1
Gleick and Cooley
83
USA
Quantification of key energy
inputs for bottled water
Manufacturing of bottle
Treatment of water
Fill, label, seal
Transportation
Cooling
4.0
0.0001–0.02
0.01
1.4–5.8
0.2–0.4
MJl
–1
MJl
–1
MJl
–1
MJl
–1
MJl
–1
Vince et al.
80
Unspecified
LCA of electricity in potable
water-treatment processes
Ultrafiltration plant
Reverse osmosis plant
0.8
4.9
kWhm
–3
kWhm
–3
Stokes & Horvath
18
California
Energy use and emissions
of different water supply
systems using LCA,
commercial databases and
economic calculations
Imported water
Desalinated ocean water
Desalinated brackish groundwater
Recycled water
1,093
2,395–2,465
1,628
1,023
gCO
2
em
–3
gCO
2
em
–3
gCO
2
em
–3
gCO
2
em
–3
Racoviceanu et al.
84
Toronto
LCA of municipal water-
treatment system
Chemical manufacturing
Chemical transportation
Water-treatment facility
8.87
1.95
117.31
gCO
2
em
–3
gCO
2
em
–3
gCO
2
em
–3
Cohen et al.
30
San Diego County,
USA
Quantification of water-
related energy use
Supply and treatment
Residential end use
Commercial, industrial and
institutional end use
Wastewater treatment
80–4,200
0–27,200
0–67,700
130–980
kWhacrefoot
–1
kWhacrefoot
–1
kWhacrefoot
–1
kWhacrefoot
–1
Klein et al.
31
California, USA
California’s energy–water
relationship
Water supply/conveyance
Water treatment
Water distribution
Wastewater collection and
treatment
Wastewater discharge
Recycled-water treatment and
distribution
0–14,000
100–16,000
700–1,200
1,100–4,600
0–400
400–1,200
kWhMG
–1
kWhMG
–1
kWhMG
–1
kWhMG
–1
kWhMG
–1
kWhMG
–1
Goldstein and Smith
4
USA
Analysis of electricity
consumption for water supply
and treatment
Surface-water treatment
Wastewater treatment
0.371–0.392
0.177–0.780
kWhm
–3
kWhm
–3
Griffiths-Sattenspiel
and Wilson
10
USA
Analysis of the carbon
footprint of the water sector
Heating of residential water 0–203,600 kWhMG
–1
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Although many studies call for a greater focus on the issue to
give stakeholders better understanding of the water sectors energy
prole and for governments to make more informed water-policy
choices
18,28,32,33
, comprehensive analyses remain limited, and esti-
mates are mostly to be found in the grey literature.
Energy use associated with agricultural water use. Globally,
irrigation accounts for around 20% of the arable land area, but
contributes 40% of the global harvest
34
. Studies on climate change
impacts on agriculture generally project that the demand for water
for crop production will increase with higher temperatures and
greater variability of precipitation (for example, refs34–38). Many
developing countries, for example those in sub-Saharan Africa,
face signicant challenges in achieving and maintaining food
security. Some studies see expansion of irrigated agriculture to be
necessary to meet future demand and to achieve growth in the
agricultural sector
34,39
. is will require more water and in many
cases more energy for abstraction, transportation and application
to crops.
On a global scale, over 3,800km
3
of fresh water is withdrawn
each year, of which about 70% is used in the agriculture sector,
primarily for irrigation
40
. e top abstractors are India, China
and the US, with withdrawals of 646, 550and 477km
3
per year,
respectively
41
. Figure 4 illustrates the sectoral distribution of
water withdrawals in the top three countries and in the UK: for
the large irrigator countries, the largest proportion of fresh water
is used in agriculture, compared with less than 3% in the UK.
Such structural dierences, together with dierences in reliance
on groundwater, have important implications for present and
future energy use. is is apparent in a region such as California
where agriculture uses 80% of the state water supply, and 90% of
all electricity used on farms is consumed in pumping groundwa-
ter for irrigation
30
.
Irrigation can involve substantial use of energy for pumping
and delivering water to crops. Energy use directly relates to the
depth or distance over which the water is pumped; examples from
Asia show that the energy consumed in irrigated rice production
can be twice as high as in rain-fed rice, and groundwater irriga-
tion can be 25% more energy intensive than surface-water irri-
gation, owing to the force that is required to li water
15,42
. Since
the 1960s, the global withdrawal of groundwater has increased
rapidly from around 150km
3
to 1,000km
3
(ref.43) and the irri-
gated land area has doubled from 138.8×10
6
ha to 277.1×10
6
ha
(ref. 40). Hence, the energy use and carbon footprint of water
use in agriculture have become increasingly important
13,14
,
and are becoming recognized through concepts such as virtual
water (the water used in production of services or goods)
44
and
waterfootprints
45
.
During the past six decades, the energy-consumption patterns
of agriculture have changed enormously
46,47
, and today the sector is
one of the main contributors of GHG emissions
24,48
. Studies on direct
energy use in farm operations show that irrigation plays a dominant
role
42,48–50
. e operational processes involving energy for irriga-
tion are abstraction and application of water. However, many fac-
tors within each process inuence energy intensity (Fig.5). Energy
use varies with the source of water (groundwater, surface water and
water stored in reservoirs), the distance and li over which water is
transported before application, and the application method (in the
case of pressurized systems). In addition, the intensity of water use
in irrigated agriculture is a critical factor determining the amount
of water and thereby the energy required for irrigation. Pumping
water is the most energy-demanding process. According to a basic
theoretical physical relationship, the energy required to li 1m
3
of
water (with a density 1,000kgm
–3
) through 1m at 100% eciency
is 0.0027kWh:
It is this intractable property of water that underpins the close
relationship between water management and energy use; water is
heavy, and management oen requires its transport, sometimes
over long distances. To obtain a more precise calculation, detailed
knowledge of the pumping system (li, pump eciency, pipe fric-
tion, system pressure and so on
51
), and transmission and distribution
losses of the power supply system is required. is is particularly the
case for electricity, where losses can be considerable
11
.
Perhaps unsurprisingly, given the rapidly increasing demand,
the water–energy nexus of agricultural water has received more
attention in South Asia than many other parts of the world
32
. In
some regions of India, almost half of all energy produced is used
for irrigation
32,52,53
. e boom in energy use within agriculture is
related to the green revolution, particularly as South Asia rapidly
adopted technology to abstract groundwater for irrigation
54
. is,
Water supply
Irrigation supply
Wastewater treatment
End use
Figure 2 | Distribution of carbon emissions from energy use in the US
water sector (%). Data from ref.10.
Rivers, lakes,
reservoirs and
groundwater
Clean–water
supply and treatment to
potable standard
1 Mt CO
2
e
Direct
abstraction
Agriculture, industry,
commerce and so on
Leakage
0.4 Mt CO
2
e
Water company
admin and
transport emissions
0.2 Mt CO
2
e
Clean–water distribution
0.6 Mt CO
2
e
Household water use
35 Mt CO
2
e
Non–household
water use
?
Wastewater treatment
2.1 Mt CO
2
e
Wastewater pumping
and collection
(including urban runo)
0.2 Mt CO
2
e
Sludge to land
1–2 Mt CO
2
e
Discharge to water bodies
15,353
Ml d
–1
3,683
Ml d
–1
8,726
Ml d
–1
20,800
Ml d
–1
3,576
Ml d
–1
?
?
Figure 3 | Water flow and greenhouse-gas emissions from the UK water
sector, 2005–06. Reproduced with permission after ref.8. © 2008
Crown Copyright.
Energy (kWh) =
9.8 (m s
–2
) × li (m) × mass (kg)
3.6 × 10
6
× eciency (%)
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among other factors, has quadrupled the area under groundwater
irrigation in India since 1950 (ref.54). Emissions from groundwater
pumping for irrigated rice in India were 58.7 million tonnes CO
2
e
in 2000 (ref.15), and estimates of Indias average total liing irriga-
tion economy amounted to 94 million tonnes CO
2
e per year (6% of
Indias total GHG emissions)
11
.
China is also rapidly developing its groundwater abstraction and
water transport. e electrical intensity (MWhm
–3
) of water pro-
duction and supply has increased nearly 20% from 1997to 2005
(ref.55). Analysis of Chinas water–energy nexus found that agricul-
ture is not only the heaviest water user but also the least water-e-
cient sector
55
. Uneven distribution of water resources exacerbates
this situation. Of Chinas cultivated land area, 56% lies north of the
Yangtze River, but this area possesses only 17% of Chinas total water
resources
55
. Considering that around 40% of Chinas cultivated land
area is irrigated, the northern part of China, in particular, has come
to rely heavily on groundwater for irrigation. As groundwater has
been a weakly regulated resource in China, abstraction has increased
rapidly
56
. Between 1978and 2003, the number of groundwater tube-
wells across China more than doubled
56
, and this massive expansion
of groundwater abstraction has led to falling groundwater tables,
environmental problems and increased energy use
57
. To compensate
for the lack of water resources in northern China, large-scale water
transfer schemes from the south are being established, which will
involve high energy costs for construction, maintenance and pump-
ing. Furthermore, water from the southeastern part of the country
is heavily polluted and needs extensive treatment and monitoring
58
.
In our systematic review we found several studies dealing with
energy use in agriculture, with irrigation included as part of a
comprehensive assessment. Most studies examine both direct and
indirect energy use, but they do not always distinguish between the
two (for example, indirect energy used for production of chemi-
cal fertilizer and direct energy as diesel fuel for farm machinery).
Presenting a total energy use in agriculture without further speci-
cation makes it dicult to determine the relative importance of
irrigation. Further, it is dicult to compare studies, as some include
factors such as manufacturing and maintenance costs and others do
not. Moreover, the use of dierent units for energy use (for exam-
ple, kWhha
–1
or MJmm
–1
) further complicates comparison. Studies
containing more specic estimates of energy use for irrigation and
associated GHG emissions are presented in Table2. ose with a
stronger focus on irrigation concentrate on regions with greater
dependence on irrigated agriculture, such as Asia and the Middle
East. Many of the results look similar; however, the average of the
15 numbered studies is 8,529 MJ ha
–1
with a standard deviation
of 6,513MJ ha
–1
(Fig. 6). In a review
49
of carbon emissions from
farm operations, the energy use for irrigation ranges from roughly
3,000to 130,000MJha
–1
. ese signicant disparities reect dier-
ences in the agricultural systems as well as regional environmental
conditions, but are also due to the complexity of, and data require-
ments for, estimating energy use for irrigation.
ere are many challenges to generating standardized compa-
rable estimates. First, groundwater levels vary between and within
regions, and by seasons and year. As pumping of groundwater is
the most energy-intensive process in irrigation, information on
water li (total dynamic head) is crucial in estimating energy use.
Most of the studies we reviewed make simple assumptions about
li across regions and nations (that is, they are not based on survey
data). Furthermore, global standardized intensities for crop water
use are used instead of more local-based information, and few stud-
ies include information on pump technology and power source. For
these reasons, energy-use estimates are relatively crude, especially
at national or international scales. Generally, only electricity use is
included, with few studies covering dierent energy sources (for
example, petrol (gasoline) or diesel) or the proportion of energy
supply that comes from renewable sources — information that is
critical for converting energy use to GHG emissions. ere are sig-
nicant dierences between the carbon densities of dierent energy
sources as well as the electricity generated in dierent countries or
by die,rent power plants. ese details are generally omitted or
standard carbon conversion factors are applied.
Together, the large number of important factors, assumptions
and dierences in site conditions lead to widely ranging results
between studies. is makes comparisons of GHG emissions from
irrigation dicult and estimates of aggregate estimates of energy
use relatively crude.
Towards integration of energy and water
Regulatory action and behaviour change. Our systematic review
identies a knowledge gap at the interface between research on
water and on energy, and a separation of water and energy policies.
ese problems exist in part because of lack of standardized meth-
odology and because data are not easily accessible
59
. Consistent and
systematic denitions of water-sector boundaries are necessary.
Greater integration would allow the water industry to take advan-
tage, within a regulated regime, of its ability to generate renewable
energy and use it to defray energy-intensive processes within the
sector
7
. Likewise, clean technologies for providing water and waste-
water services must be explored further
60
.
Unfortunately, the lack of modernization of water-sector tech-
nology to improve water and energy eciency is evident. In the
UK, water companies’ investments in research and development
have decreased 60% from 1999to 2008 (according to 2008 prices),
and government research-and-development schemes for the water
sector are very limited compared with the energy sector
7
. In the
US, failure to integrate energy issues in decision-making on water
policy has been noted, and such integration is long overdue
30
. We
need to advance the understanding of water–energy relationships
to develop tools and mechanisms that will aid in accounting for
and reducing GHG emission. It has been argued that analysing the
energy use and emissions of dierent water supply systems using an
approach that combines LCA, commercial databases and economic
calculations will have greater eect on decision-making processes,
because it includes energy consumption and material use in the
analysis
18
. Problems also arise because of the lack of data on energy
use in the water sector
10
. It is important to understand the broader
Abstraction
of water
Application
of water
Total dynamic head
Pump/motor type
Eciency
Water purity
Power source
T and D losses
Transport
T and D losses
Irrigation system
Pipe system
Power source
Eciency
Climate
Topography
Soil
Crop type
Agricultural
management
Water–use
intensity
Figure 4 | Freshwater withdrawals by sector in 2000 (%). Data from ref.41.
Figure 5 | Overview of factors aecting energy use for groundwater
irrigation. T and D, transmission and distribution.
USAUK India China
Agricultural Industrial Municipal
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implications of supplying water or achieving certain water-quality
standards. A rst estimate from the UK
6
indicates that, without
intervention, achieving the higher water-quality standards required
by the European Water Framework Directive could increase CO
2
emissions by 110,000tonnes per year. It is expected that develop-
ing countries will go through similar patterns of higher-quality
standards, better pollution control and longer-distance distribu-
tion as seen in other parts of the world
61
. is will contribute to
increases in water-related energy use. For example, with an already
very high fraction (78%) of available water, China is facing chal-
lenges
62
, because the combination of inadequate water supply and
increasing environmental degradation may result in actions that
are inconsistent with mitigation policies
63
.
Recently, the UK government launched a new strategy for the
water sector (Future Water) that also includes mitigation tar-
gets
8
. e strategy sets out the need for the sector to contribute to
Table 2 | Overview of studies on energy use and GHG emissions in irrigation agriculture.
Study no. Author and region Methods Results (estimate) Units
Lal
49
Various
Review of studies estimating energy use in farm
operations to assess carbon emissions
5.16±3.9 kg CEcm
–1
1 Vlek et al.
50
Developing regions
Assess the energy use of various practices in tropical
agriculture in terms of contribution to CO
2
emissions
6,666–10,000
0.66–0.74
MJha
–1
t CO
2
ha
–1
2 Singh et al.
85,86
India
Mathematical analysis of relationship between
energy inputs and yields in different
agro-climate zones
890–6,003
21–329
1.2–10.3
MJha
–1
kWhha
–1
lha
–1
3 Shah
11
India
National estimation of carbon emissions from
irrigation pumping
3,245–9,405
0.13–1.06
MJha
–1
tCha
–1
Nelson et al.
15
India*
Calculation of present and future CO
2
emissions from
groundwater pumping under four scenarios
300.5 t CO
2
em
–1
Pathak & Wassmann
87
Haryana, India
Presenting a modelling tool to assess emission of
GHGs from the agricultural sector as affected by
land-use and residue-utilization options
0.05 kg Cha
–1
mm
–1
4 Khan et al.
14
Murray Darling Basin, Australia
Quantification of indicators in wheat, rice, and barley
production and irrigation systems to estimate and
reduce carbon footprint
1,372–13,313
0.37–2.54
MJha
–1
kWhm
–3
5 Jackson et al.
82
Australia
Comparative analysis of water application and
energy consumption in different irrigation systems
and crops
3,186–41,759 MJha
–1
Maraseni et al.
88
Darling Down, Australia
Estimation of GHG emission from three types of
cotton farming systems
1,329 kg CO
2
ha
–1
Yaldiz et al.
89
Turkey
Analysis of energy use in field crop production 0.63 MJm
–3
6 Erdal et al.
90
Tokat region, Turkey
Energy use and economic analysis of sugar
beet production
1,883 MJha
–1
7 Çiçek et al.
91
Tokat region, Turkey
Energy consumption patterns and economic analysis
of irrigated and rain-fed wheat production
1,944 MJha
–1
8 Topak et al.
92
Anatolia–Konya, Turkey
Comparison of energy of irrigation regimes in sugar
beet production
11,713–23,764 MJha
–1
9 Acaroglu and Aksoy
93
Anatolia–Konya, Turkey
Analysis of energy balance in production of
Miscanthus giganteus
2,652
1.02
MJha
–1
MJm
–3
10 Mohammadi et al.
94
Ardabil, Iran
Economic analysis of energy consumption in
potato production
11,368 MJha
–1
11 Shahan et al.
95
Ardabil, Iran
Energy use and economic analysis of
wheat production
4,230 MJha
12 Pervanchon et al.
96
France (intensive system)
Energy indicator calculating energy consumption to
evaluate environmental impacts of
agricultural systems
7,766 MJha
–1
13 Rodrigues et al.
97
Alentejo, Portugal
Relating energy performance and water productivity
of three crops under sprinkler irrigation
15,800–19,800 MJha
–1
14 Moreno et al.
98
Castilla-La Mancha, Spain
Evaluation of proposed measures for improving
energy efficiency in irrigation delivery systems
1,626–22,428 MJha
–1
Dalgaard et al.
99
Denmark
Assess energy use in conventional and organic
agriculture at field-operational, crop-type, and
national level
52 MJmm
15 Tzilivakis et al.
100
United Kingdom
Assess global warming potential of sugar beet
production and calculate output/input ratios
2,600 MJha
–1
Results present energy use or emissions from irrigation only. Study number refers to Fig.6. CE, carbon equivalent.
*Study not peer-reviewed.
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achieving the Climate Change Act 2008 target of an 80% reduction
in GHG emissions by 2050. is new strategy requires water
companies to provide details of their annual GHG emissions and
include carbon costs in evaluations of future investment options
6,8
.
e water sector is also being included in an industry carbon-trad-
ing scheme called Carbon Reduction Commitments, and Water
UK, a representative organization for all water and wastewater
service suppliers, has voluntarily committed to ensure that at least
20% of all energy used by the water industry comes from renew-
able sources by 2020 (ref.8). However, the new UK regulations for
mitigation exclude some of the most signicant parts of the water
sector. Despite end use accounting for the highest energy use in
the water sector, no regulations or requirements have been made
to control GHG emissions from this part of the sector. Whereas
regulations for building standards and room heating exist, legis-
lation to ensure energy eciency for water in the home is lack-
ing. Without regulatory pressure, there is a risk that new-build UK
housing will have higher GHG emissions from water heating than
existing housing
64
. is disregard of the importance of consumer
behaviour and demand management is evident in policy as well as
in the published literature. e exception is subsidies, which is the
only such aspect well covered.
In the UK, two sources have published research in connection
with the new regulations. e Environment Agency has published
a report on the future carbon cost of water-sector management
options
65
together with a number of reports to help identify path-
ways to reduce the water industry’s carbon footprint by 2050 (ref.6).
UK Water Industry Research has published reports on carbon
accounting and mitigation to guide best practice in the water indus-
try
66
. Such progressive steps in regulation may help to initiate more
research on the topic, not only in the UK but worldwide.
Other activities to promote energy eciency in the water sec-
tor are taking place, especially in areas struggling with water
energy problems, such as the southwest of the US. Both the public
and academic sectors are active in this regard (see Supplementary
Table S2). Two studies of energy saving in wastewater in the US
show that optimized aeration and improved pumping could save
5471,057 million kWh per year
67
, and energy recovery from anaer-
obic digestion could save 628–4,940 million kWh per year
68
. e
co-benets of saving water are also important to consider, especially
when evaluating technologies and management options for water
conservation. A study of measures for urban water conservation
in California found that some water-saving household appliances
only prove cost-eective when energy savings are included
69
.is
opportunity also applies to irrigated agriculture, where many water
conservation programmes exist that would benet from greater
focus on complementary energy savings. A UK study found that
supply-side measures (such as increasing abstraction, new reser-
voirs and water transfer) generally resulted in an increase in emis-
sions and that most demand management options (such as water
metering) had low operational emissions
65
.
In terms of public understanding and behaviour change, there
is potential to raise awareness about the linkages between water
and energy and to modify carbon/water footprinting approaches
to realize co-benets. e Pacic Institute has developed a freely
available Water to Air model for the industry to quantify energy
use of its water supply systems and a website for the private con-
sumer, WECalc, a home water–energy–climate calculator (see
Supplementary Table S2). WECalc provides a detailed analysis of
domestic water use, related energy use and GHG emissions based
on user inputs. e calculator compiles information on energy
intensities for water-related processes in the household from a large
range of sources. is is a good example of how to target end use
and promote both water saving andmitigation.
Meeting future challenges. e ‘perfect storm
70
scenario of sus-
taining increases in food production given climate change impacts
and the need to reduce GHG emissions, together with increasing
competition for water, provides a strong rationale for better inte-
gration of water and energy use. Worldwide, food production is
projected
34
to increase by 50% by 2030, at the cost of considerable
increases in irrigated area and water use
39
. According to projec-
tions from the United Nations Food and Agriculture Organization,
developing countries account for 75% of the global irrigated area
and are likely to expand their irrigated areas by 0.6% per year until
2030 (ref.34). ese estimates exclude the eects of climate change,
which in many cases may put further pressure on water resources
22
.
e demand for irrigation water is likely to increase further with
higher temperatures and greater variability of precipitation
34–38,71
.
For example, Chinas net irrigation requirements are projected to
increase 2–15% by 2020 (ref.35). With increased irrigation, further
development of groundwater is highly likely. Declining groundwa-
ter level will compound energy use, as deeper wells require more
carbon-intensive electric-driven pumps.
In countries already struggling with water scarcity, climate
change is creating further uncertainty in water governance that
requires accelerated research to avoid water-related stresses
14
.
Research on planning or mainstreaming adaptation in water man-
agement is growing
72–74
. However, few studies consider in detail
the energy implications of adaptation measures, and there is a
need to achieve better linkage between mitigation and adaptation.
Consideration of alternative water supply systems, treatment tech-
nologies or water allocation may have a tendency to overlook the
carbon cost; some measures regarded as sustainable water man-
agement, such as desalination, are very energy intensive
63
. is is
particularly the case in the absence of regulatory pressure, as is cur-
rently the case in mostcountries.
Biofuel production involves both ‘water for energy’ and ‘energy
for water’, and may exacerbate stresses on water and food secu-
rity. Although biofuels in principle are aimed at mitigating climate
change, their production has signicant implications for energy use
because of their water requirements, which compared with equiva-
lent amounts of energy produced by other methods, can be relatively
high
75,76
. Potential trade-os between biofuel and food production
have been noted in various studies
77,78
. China, for instance, ranks
among the worlds top three ethanol producers (3.6 billion litres),
using 1.1% of its cropped area for biofuel production which is
2.2% of its total agricultural water withdrawals
79
. In China alone,
the demand for oil is expected to double by 2030, and to meet this
demand China set a goal of producing 17.7 billion litres of biofuel
123456789101112131
41
5
Study no.
45
40
35
30
25
15
10
5
0
GJ ha–
1
Figure 6 | Energy use for irrigation. This shows the results of the studies
reviewed (study number refers to Table2). Only 15 of the 21 studies
have units that allow direct comparison. Where a range is presented, the
average is based on the lowest and highest energy-use estimate in that
study. Variations reflect dierences in agricultural systems, environmental
conditions and methodology.
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in 2030 (ref.79). A study from the US
80
also highlights the potential
of increased nitrate contamination and estimates that the impact of
biofuel production on energy use for drinking-water treatment may
be an additional 2,360 million kWh per year.
Agricultural management practices strongly inuence the inten-
sity of water use and thereby energy use for irrigation. Water-use e-
ciency varies with dierent irrigation systems (ood, drip, sprinkler
and so on) and owing to the higher degree of control, pressurized
systems are generally more water ecient than ood irrigation
81
. An
assessment of energy and water trade-os in enhancing food secu-
rity emphasizes that a change from surface water to groundwater
irrigation will increase energy use
42
. Yet water-use intensity seems
to be lower in groundwater irrigation owing to greater adoption of
irrigation-system technologies. A study from Australia
82
shows that
converting from ood to pressurized systems results in a reduction
in water use of between 10% and 66%. Using pressurized systems in
groundwater irrigation could reduce energy consumption by 12%
to 44%, but in surface water irrigation, pressurized systems may
result in an energy increase by up to 163% (ref.82). Promotion of
irrigation-system technologies as a method of saving both water
and energy may be hampered by unregulated and under-priced
water resources—in California, for example, this is discouraging
investments in more ecient irrigation systems
81
. ere seems to
be potential to reduce energy use in groundwater irrigation with
the right management practices and the use of pressurized irriga-
tion systems. Outcomes will, however, depend on many factors,
and a comprehensive synthesis of practical experience in energy
use and water-saving measures would help to guide practitioners
andregulators.
Conclusion
Energy use in the water sector is associated with abstraction, con-
veyance and treatment of fresh water and wastewater, together
with end-use processes (particularly heating of water). Our sys-
tematic review shows that energy use and GHG emissions in the
sector are under-recognized, in part because of dierences in the
scope of water-sector boundaries, data availability, methodologi-
cal approaches and whether results are expressed as energy use or
GHG emissions. Although end use oen has the highest energy
use of all water-sector elements, it has not traditionally been seen
as a direct part of the water sector and is oen unaccounted for in
water management and policy. e relative paucity of information
and analysis of energy use emphasizes the need for policy coherence
and innovative responses in water management if we are to meet
sustainabilitygoals.
Although results of assessments in the sector are becoming
available, these are generally limited to the grey literature (less so
for irrigation water use). Progress in the UK and the US, notably
California, has been primarily in response to regulatory require-
ments to monitor and reduce GHG emissions in the water industry,
and to growing concern about water and energy security. In coun-
tries with extensive groundwater-based irrigation such as India and
China, concern about energy use and access has stimulated interest
in the issue. What evidence there is shows that energy use in the
water sector is considerable and growing. is growth is likely to
continue, sometimes as an unintended policy outcome, with greater
pressure to use and maintain quality of water resources. Despite
some recent progress, we need to better understand and prole the
role of the water sector as a GHG emitter. A coordinated view of the
water sector, with clear sector boundaries, will promote more com-
prehensive assessments of energy use. Standardized methodologies
will enable comparisons between assessments of dierent technolo-
gies and processes, and between regions or countries.
e water sector faces great challenges during the coming dec-
ades. Greater focus on its energy requirements will be a crucial part
of the policy response to these challenges.
References
1. King, C.W., Holman, A.S. & Webber, M.E. irst for energy. Nature Geosci.
1, 283–286 (2008).
2. Curlee, T.N. & Sale, M.J. in Conf. Water Security in the 21st Century, 22
(Environmental Science Division, 2003).
3. US Department of Energy Energy Demands on Water Resources (US
DOE, 2006).
4. Goldstein, R. & Smith, W. Water and Sustainability: US Electricity
Consumption for Water Supply and Treatment: e Next Half Century (Electric
Power Research Institute, 2002).
5. Gleick, P.H. Water and energy. Annu. Rev. Energ. Environ.
19, 267–299 (1994).
6. Ainger, C. et al. A Low Carbon Water Industry in 2050 (Environment
Agency, 2009).
7. Council for Science & Technology Improving Innovation in the Water Industry:
21st Century Challenges and Opportunities (CST, 2009).
8. Department for Environment Food and Rural Aairs Future Water. e
Government’s Water Strategy for England (Stationery Oce, 2008).
9. UK Water Industry Research Energy Eciency in the UK Water Industry: A
Compendium of Best Practices and Case Studies (UK WIR, 2010).
10. Griths-Sattenspiel, B. & Wilson, W. e Carbon Footprint of Water (River
Network, 2009).
11. Shah, T. Climate change and groundwater: Indias opportunities for mitigation
and adaptation. Environ. Res. Lett. 4, 035005 (2009).
12. http://water-energy.lbl.gov/node/10
13. Khan, S. & Hanjra, M.A. Footprints of water and energy inputs in food
production: global perspectives. Food Policy 34, 130–140 (2009).
14. Khan, S., Khan, M.A., Hanjra, M.A. & Mu, J. Pathways to reduce the
environmental footprints of water and energy inputs in food production. Food
Policy 34, 141–149 (2009).
15. Nelson, G.C. et al. Greenhouse Gas Mitigation. Issues for Indian Agriculture.
Vol. I FPRI Discussion Paper 00900 (International Food Policy Research
Institute, Environment and Production Technology Division, 2009).
16. Frijns, J. Towards a common carbon footprint assessment methodology for the
water sector. Wat. Environ. J. 25, doi:10.1111/j.1747–6593201100264.x (2011).
17. Friedrich, E., Pillay, S. & Buckley, C.A. e use of LCA in the water industry
and the case for an environmental performance indicator. Wat. SA
33, 443–451 (2007).
18. Stokes, J.R. & Horvath, A. Energy and air emission eects of water supply.
Environ. Sci. Technol. 43, 2680–2687 2009).
19. Vörösmarty, C.J., Green, P., Salisbury, J. & Lammers, R.B. Global water
resources: Vulnerability from climate change and population growth. Science
289, 284–288 (2000).
20. Harte, J. & Elgasseir, M. Energy and water. Science 199, 623–634 (1978).
21. Hightower, M. & Pierce, S.A. e energy challenge. Nature
452, 285–286 (2008).
22. IPCC Technical Paper on Climate Change and Water (eds Bates, B.,
Kundzewicz, Z.W., Palutikof, J. & Wu, S.) (IPCC Secretariat, 2008).
23. IPCC Climate Change 2007: Mitigation (eds Metz, B. et al.) (Cambridge Univ.
Press, 2007).
24. Smith, P. et al. Policy and technological constraints to implementation of
greenhouse gas mitigation options in agriculture. Agr. Ecosyst. Environ.
118, 6–28 (2007).
25. Lofman, D., Petersen, M. & Bower, A. Water, energy and environment nexus:
e California experience. Int. J.Wat. Resour. Dev. 18, 73–85 (2002).
26. Abbott, M. & Cohen, B. Productivity and eciency in the water industry. Util.
Policy 17, 233–244 (2009).
27. Cederwall, W., Shady, A. & Bjorklund, G. Workshop 4 (synthesis): Bridge
building between water and energy. Wat. Sci. Technol.
45, 149–150 (2002).
28. Zakkour, P.D., Gochin, R.J. & Lester, J.N. Evaluating sustainable energy
strategies for a water utility. Environ. Technol. 23, 823–838 (2002).
29. Zakkour, P.D., Gaterell, M.R., Grin, P., Gochin, R.J. & Lester, J.N.
Developing a sustainable energy strategy for a water utility. Part I. A review of
the UK legislative framework. J. Environ. Manage. 66, 105–114 (2002).
30. Cohen, R., Nelson, B. & Wol, G. Energy Down the Drain. e Hidden Costs
of Californias Water Supply (Pacic Institute & Natural Resources Defense
Council, 2004).
31. Klein, G. California’s Water–Energy Relationship (California Energy
Commission, 2005).
32. Malik, R.P.S. Water–energy nexus in resource-poor economies: e Indian
experience. Int. J.Wat. Resour. Dev. 18, 47–58 (2002).
33. Zakkour, P.D., Gaterell, M.R., Grin, P., Gochin, R.J. & Lester, J.N.
Developing a sustainable energy strategy for a water utility. Part II. A review of
potential technologies and approaches. J.Environ. Manage. 66, 115–125 (2002).
34. Bruinsma, J. (ed.) World Agriculture: Towards 2015/2030. An FAO Perspective.
(Earthscan, 2003).
REVIEW ARTICLE
NATURE CLIMATE CHANGE DOI: 10.1038/NCLIMATE1147
© 2011 Macmillan Publishers Limited. All rights reserved
NATURE CLIMATE CHANGE | ADVANCE ONLINE PUBLICATION | www.nature.com/natureclimatechange 9
35. Döll, P. Impact of climate change and variability on irrigation requirements:
A global perspective. Climatic Change 54, 269–293 (2002).
36. Fischer, G., Tubiello, F.N., van Velthuizen & Wiberg, D.A. Climate Change
Impacts on Irrigation Water Requirements: Eects of Mitigation, 1990–2080
(IIASA reprint, 2007).
37. Rosenberg, N.J., Brown, R.A., Izaurralde, R.C. & omson, A.M. Integrated
assessment of Hadley Centre (HadCM2) climate change projections on
agricultural productivity and irrigation water supply in the conterminous United
States. I. Climate change scenarios and impacts on irrigation water supply
simulated with the HUMUS model. Agr. Forest Meteorol. 117, 73–96 (2003).
38. Xiong, W. et al. Climate change, water availability and future cereal production
in China. Agr. Ecosyst. Environ. 135, 58–69 (2010).
39. Sauer, T. et al. Agriculture and resource availability in a changing world: e
role of irrigation. Wat. Resour. Res. 46, W06503 (2010).
40. World Resource Institute Earth Trends: Environmental Information (WRI,
2000); available at http://earthtrends.wri.org/index.php.
41. United Nations Food and Agriculture Organization Land and Water Division
Weblink: FAO AquaSTAT (FAO, 2000).
42. Mushtaq, S., Maraseni, T.N., Maroulis, J & Hafeez, M. Energy and water
tradeos in enhancing food security: A selective international assessment.
Energ. Policy 37, 3635–3644 (2009).
43. Shah, T. et al. in Water for Food, Water for Life (ed. Molden, D.) Ch. 10
(Earthscan, 2007).
44. Allan, J.A. Virtual water: a strategic resource global solutions to regional
decits. Ground Water 36, 545–546 (1998).
45. Hoekstra, A.Y. & Hung, P.Q. Globalisation of water resources: international
virtual water ows in relation to crop trade. Glob. Environ. Change A
15, 45–56 (2005).
46. Cleveland, C.J. e direct and indirect use of fossil fuels and electricity in
USA agriculture, 1910–1990 Agr. Ecosyst. Environ. 55, 111–121 (1995).
47. Leach, G. Energy and food-production. Food Policy 1, 62–73 (1975).
48. Devi, R. Energy consumption pattern of a decentralized community in
northern Haryana. Renew. Sustain. Energ. Rev. 13, 194–200 (2009).
49. Lal, R. Carbon emission from farm operations. Environ. Int. 30, 981–90 (2004).
50. Vlek, P.L.G., Rodriguez-Kuhl, G. & Sommer, R. Energy use and CO
2
production in tropical agriculture and means and strategies for reduction or
mitigation. Environ. Dev. Sust. 6, 213–233 (2004).
51. Whien, H.H. Energy Eciency and Environmental News: Energy Use
In Irrigation, in Florida Energy Extension Service (Institute of Food and
Agricultural Sciences, Univ. Florida, 1991).
52. Gupta, R.K. Water and energy linkages for groundwater exploitation: A case
study of Gujarat state, India. Int. J.Wat. Resour. Dev.18, 25–45 (2002).
53. Singh, H., Mishra, D., Nahar, N.M. & Ranjan, M. Energy use pattern in
production agriculture of a typical village in and zone India: part II. Energ.
Convers. Manage. 44, 1053–1067 (2003).
54. Shah, T., Roy, A.D., Qureshi, A.S. & Wang, J. Sustaining Asias groundwater
boom: An overview of issues and evidence. Nat. Resour. Forum
27, 130–141 (2003).
55. Kahrl, F. & Roland-Holst, D. Chinas water-energy nexus. Wat. Policy
10 (Suppl. 1), 51–65 (2008).
56. Wang, J., Huang J., Rozelle, S., Huang, Q. & Blanke, A. Agriculture and
groundwater development in northern China: Trends, institutional responses,
and policy options. Wat. Policy 9 (Suppl. 1), 61–74 (2007).
57. Khan, S., Hanjra, M.A. & Mu, J. Water management and crop production for
food security in China: A review. Agr. Wat. Manage. 96, 349–360 (2009).
58. Xuejun, S., Hong, W. & Zhaoyin, W. Interbasin transfer projects and their
implications: A China case study. Int. J.River Basin Manage. 1, 5–14 (2003).
59. Goldstein, N.C. et al. e energy–water nexus and information exchange:
challenges and opportunities. Int. J.Water 4, 5–24 (2008).
60. World Business Council for Sustainable Development Water, Energy and Climate
Change. A Contribution from the Business Community (WBCSD, 2009).
61. Friedrich, E., Pillay, S. & Buckley, C.A. Carbon footprint analysis for
increasing water supply and sanitation in South Africa: a case study. J.Cleaner
Prod. 17, 1–12 (2009).
62. Amarasinghe, U.A., Giordano, M., Liao, Y. & Shu, Z. Water Supply, Water
Demand and Agricultural Water Scarcity in China: A Basin Approach. CPSP
Rep. 11. Vol. Country Policy Support Program (CPSP) (International Water
Management Institute, International Commission on Irrigation and
Drainage, 2005).
63. Mata, L.J. & Budhooram, J. Complementarity between mitigation and
adaptation: the water sector. Mitig. Adapt. Strategies Glob. Change
12, 799–807 (2007).
64. Clarke, A., Grant, N. & ornton, J. Quantifying the Energy and Carbon Eects
of Water Saving (Environment Agency, 2009).
65. Reold, E., Leighton, F. Choudhury, F. & Rayner, P.S. Greenhouse Gas
Emissions of Water Supply and Demand Management Options Science Report
SC070010 (Environment Agency, 2008).
66. UK Water Industry Research Reports on Climate Change and the Water
Industry (UK WIR, 2010); available via www.ukwir.org/site/web/content/
reports/reports?FolderId=90265.
67. Hoppock, D.C. & Webber, M.E. Energy needs and opportunities at POTWs
in the United States. Proc. Am. Soc. Mech. Eng. (ASME) 2nd Int. Conf. Energy
Sustain. (2008).
68. Stillwell, A.S., Hoppock, D.C. & Webber, M.E. Energy recovery from
wastewater treatment plants in the United States: a case study of the energy–
water nexus. Sustainability 2, 945–962 (2010).
69. Gleick, P.H. et al. Waste Not, Want Not: e Potential for Urban Water
Conservation in California (Pacic Institute for Studies in Development,
Environment, and Security, 2003).
70. Godfray, H.C.J. et al. Food Security: e challenge of feeding 9 billion people.
Science 327, 812–818 (2010).
71. Döll, P. & Siebert, S. Global modeling of irrigation water requirements. Wat.
Resour. Res. 38, 1037 (2002).
72. Charlton, M.B. & Arnell, N.W. Adapting to climate change impacts on water
resources in England: An assessment of dra Water Resources Management
Plans. Glob. Environ. Change 21, 238–248 (2011).
73. Farley, K.A., Tague, C. & Grant, G.E. Vulnerability of water supply from the
Oregon Cascades to changing climate: Linking science to users and policy.
Glob. Environ. Change 21, 110–122 (2011).
74. Subak, S. Climate change adaptation in the UK water industry: managers
perceptions of past variability and future scenarios. Wat. Resour. Manage.
14, 137–156 (2000).
75. Dominguez-Faus, R., Powers, S.E., Burken, J.G. & Alvarez, P.J. e water
footprint of biofuels: a drink or drive issue? Environ. Sci. Technol.
43, 3005–3010 (2009).
76. Gerbens-Leenes, W., Hoekstraa, A.Y. & van der Meerband, T.H. e water
footprint of bioenergy. Proc. Natl Acad. Sci. USA
106, 10219–10223 (2009).
77. McCornick, P.G., Awulachew, S.B. & Abebem, M. Water-food-energy–
environment synergies and tradeos: major issues and case studies. Wat.
Policy 10 (Suppl. 1), 23–36 (2008).
78. Rajagopal, D. Implications of Indias biofuel policies for food, water and the
poor. Wat. Policy 10 (Suppl. 1), 95–106 (2008).
79. de Fraiture, C., Giordano, M. & Liao, Y.S. Biofuels and implications for
agricultural water use: blue impacts of green energy. Wat. Policy
10, 67–81 (2008).
80. Twomey, K.M., Stillwell, A.S. & Webber, M.E. e unintended energy
impacts of increased nitrate contamination from biofulels production.
J. Environ. Monitor. 12, 218–224 (2010).
81. Cooley, H., Christian-Smith, J. & Gleick, P.H. Sustaining California Agriculture
in an Uncertain Future (Pacic Institute, 2009).
82. Jackson, T.M., Khan, S. & Hafeez, M. A comparative analysis of water
application and energy consumption at the irrigated eld level. Agr. Wat.
Manage. 97, 1477–1485 (2010).
83. Gleick, P.H. & Cooley, H.S. Energy implications of bottled water. Environ.
Res. Lett. 4, 014009 (2009).
84. Racoviceanu, A., Karney, B.W., Kennedy, C.A. & Colombo, A.F. Life-cycle
energy use and greenhouse gas emissions inventory for water treatment
systems. J.Infrastruct. Syst. 13, 261–270 (2007).
85. Singh, H., Singh, A.K., Kushwaha, H.L & Singh, A. Energy consumption
pattern of wheat production in India. Energy 32, 1848–1854 (2007).
86. Singh, S., Pannu, C.J.S. & Singh, J. Energy input and yield relations for
wheat in dierent agro-climatic zones of the Punjab. Appl. Energ.
63, 287–298 (1999).
87. Pathak, H. & Wassmann, R. Introducing greenhouse gas mitigation as a
development objective in rice-based agriculture: I. Generation of technical
coecients. Agr. Syst. 94, 807–825 (2007).
88. Maraseni, T.N., Cockeld, G. & Maroulis, J. An assessment of greenhouse gas
emissions: implications for the Australian cotton. J.Agr. Sci.
148, 501–510 (2010).
89. Yaldiz, O., Ozturk, H.H., Zeren, Y. & Bascetincelik, A. Energy use in eld
crops of Turkey. Fih Int. Congress Agricultural Machinery and Energy
(Kusadası, 1993).
90. Erdal, G., Esengun, K. & Erdal, G. Energy use and economical analysis of
sugar beet production in Tokat province of Turkey. Energy
32, 35–41 (2007).
91. Cicek, A., Altintas, G. & Erdal, G. Energy consumption patterns and economic
analysis of irrigated wheat and rainfed wheat production: Case study for Tokat
region, Turkey. J.Food Agr. Environ. 7, 639–644 (2009).
92. Topak, R., Acar, B. & Ugurlu, N. Analysis of energy use and input costs for
irrigation in eld crop production: a case study for the Konya plain of Turkey.
J.Sustain. Agr. 33, 757–771 (2009).
93. Acaroglu, M. & Aksoy, A.S. e cultivation and energy balance of Miscanthus
giganteus production in Turkey. Biomass Bioenerg. 29, 42–48 (2005).
REVIEW ARTICLE
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© 2011 Macmillan Publishers Limited. All rights reserved
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94. Mohammadi, A., Tabatabaeefar, A., Shahin, S. Raee, S. & Kayhani, A. Energy
use and economical analysis of potato production in Iran a case study: Ardabil
province. Energ. Convers. Manage. 49, 3566–3570 (2008).
95. Shahan, S., Jafari, A., Mobli, H., Raee, S. & Karimi, M. Energy use and
economical analysis of wheat production in Iran: A case study from Ardabil
province. J.Agr. Technol. 4, 77–88 (2008).
96. Pervanchon, F., Bockstaller, C. & Girardin, P. Assessment of energy use in
arable farming systems by means of an agro-ecological indicator: the energy
indicator. Agr. Syst. 72, 149–172 (2002).
97. Rodrigues, G.C., Carvalho, S., Paredes, P., Silva, F.G. & Pereira, L.S. Relating
energy performance and water productivity of sprinkler irrigated maize, wheat
and sunower under limited water availability. Biosyst. Eng.
106, 195–204 (2010).
98. Moreno, M.A., Ortega, J.F., Corcoles, J.I, Martinez, A. & Tarjuelo, J.M. Energy
analysis of irrigation delivery systems: monitoring and evaluation of proposed
measures for improving energy eciency. Irrig. Sci. 28, 445–460 (2010).
99. Dalgaard, T., Halberg, N. & Porter, J.R. A model for fossil energy use in
Danish agriculture used to compare organic and conventional farming. Agr.
Ecosyst. Environ. 87, 51–65 (2001).
100. Tzilivakis, J., Warner, D.J., May, M., Lewis, K.A. & Jaggard, K. An assessment
of the energy inputs and greenhouse gas emissions in sugar beet (Beta
vulgaris) production in the UK. Agr. Syst. 85, 101–119 (2005).
Acknowledgements
e review was conducted as part of a project funded by the UK Department for
Environment, Food and Rural Aairs: ADMIT—Harmonising adaptation and
mitigation for agriculture and water in China (Grant No. D00383, www.sain-
online.org). D.C. was partly supported through a Department for International
Development Senior Research Fellow’s position and a visiting fellowship to the
Australian National Climate Change Adaptation Research Facility. We thank
A.Milman for providing additional literature for this review. e views expressed
are those of the authors and do not represent ocial policy of DEFRA, DFID or the
UKGovernment.
Additional information
e authors declare no competing nancial interests. Supplementary information
accompanies this paper on www.nature.com/natureclimatechange.
REVIEW ARTICLE
NATURE CLIMATE CHANGE DOI: 10.1038/NCLIMATE1147
© 2011 Macmillan Publishers Limited. All rights reserved
... While many aspects of this research space have been well explored, one question that has received less attention is how climate change will affect water systems' energy use. Water systems need energy to extract, pump, treat, and distribute water with sufficient quality and pressure to end users [10][11][12][13][14][15][16], which is just one facet of the broader waterenergy nexus [17,18]. A changing climate may alter water availability, water quality, and other factors that, even for the same water demand, will lead to changes in energy use. ...
... Past studies have showed how water systems' energy footprints correlate with climate variables. Rothausen and Conway [14] suggested that water systems' energy use is likely to increase because of climate change and other factors. Globally, the most energyintensive water systems are located in places with lower average precipitation [11]. ...
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The aim of this study was to determine the input-output energy consumption and to make a cost analysis of both irrigated wheat and rainfed wheat production in Tokat province (Turkey). The results showed that the amount of energy consumed in irrigated wheat production was 13,205.90 MJ ha -1 and in rainfed wheat production was 14,134.93 MJ ha -1 . In the surveyed farm holdings, the energy input-output ratio for the irrigated wheat was 3.80, while benefit-cost ratio was 0.81. The productivity of irrigated wheat was calculated to be 3.67. The energy input-output ratio for rainfed wheat was 2.51, while the benefit-cost ratio was 0.53. The productivity of rainfed wheat was calculated to be 2.43. About 77% of the total energy inputs used in irrigated wheat production were non-renewable, while only about 23% was renewable. The total energy input used in rainfed wheat production was non-renewable 75% and 25% renewable energy. This study suggested that diesel-oil and fertilizers were not efficiently used. Intensive input use in irrigated wheat and rainfed wheat raises some problems like environmental pollution and global warming.
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