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A framework for understanding energy for water

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This article offers a framework for understanding how energy is used to meet water demand in countries. Specifically, the relationships between energy use and water scarcity, the location of renewable water resources, and aggregate water demand are explored. The article also examines how policy options such as water price reforms, agriculture subsidies and crop elimination may influence the energy use and energy intensity of water withdrawals. Conclusions suggest that while policy options exist, certain uncontrollable factors such as severe water scarcity or substantial freshwater abundance limit the ability of some countries to significantly improve the aggregate energy efficiency of water provision.
energy intensity of water (extraction and treatment) and water scarcity in a sample of countries. sources: abderrahman (2001), agenda 21 Della terra d'arneo (n.d), al-Karaghouli & Kazmerski (2013), al-mashaikhi (2011), al-mooji, Hofstetter, & renck (2013), abdel-Jawad (2001), aqualogy (http://www. aqualogy.net), aquastat (http://www.fao.org/nr/water/aquastat/data/query/), association of private Water operators (2013), australian Bureau of statistics (2014), Basharat (2012), British Geological survey (2015), Buenomena (2013), Bundesanstalt für Geowissenschaften und rohstoffe (2015), Burton (1996), campanelli, foladori, and vaccari (2013), chan (2013), china urban Water association (2012), chudaeva et al. (2008), conaGua (2014), conuee (2011), copeland (2014), Darwish et al. (2009), Department for environmental, food and rural affairs (2008), Department of environment, Water and natural resources (2014), Dimakis, colleuille, & Wong (2005), Drewes (2011), ecra (2011), el tahlawi, farrag, and ahmed (2008), encyclopedia of Desalination and Water resources (2014), entidade reguladora dos serviços de Águas e resíduos [ersar], (2012), environmental agency abu Dhabi (2014), european Benchmarking cooperation (2014), european environment agency (2014), frijns, mulder, and roorda (2008), Gaut (2010), Global Water Intelligence (2015), Godskesen, Hauschild, rygaard, Zambrano, and albrechtsen (2013), Hadian, mardiana, abdurahman, and Iman (2006), Hamed (2004), Hardy et al. (2012), Hayek (2014), Hernández-mora, martinez-corona, llamas-madurga, and custodio-Gimena (2010), Imperial Irrigation District (2015), International Groundwater resources assessment centre [IGrac] (https://ggmn.unigrac. org), Japan Waterworks association (2014), lemos, Dias, Gabarrell, and arroja (2013), ludwig (2011), Karimov et al. (2015), Kenway et al. (2008), Kumar (2013), Kwanyuen, mainuddin, and cherdchanpipat (2003), li, liu, Zheng, Han, and Hoff (2015), maas (2009), macHarg and mcclellan (2004), matar et al. (2014), mclay (2005), mcmahon and price (2011), margat and van der Gun (2013), ministry of Water & electricity (2010), ministry of Water and Irrigation (2015), nelson et al. (2008), natural resources canada Database (2014), papapetrou, Wieghaus, & Biercamp (2010), pearce (2007), peng (2014), plappally and lienhard (2012), portela and cohim (2011), Qatar General electricity and Water corporation (2014), Queensland Department of natural resources and mines (2014), raucher et al. (2010), reboucas (1999), renzoni and Germanin (2007), saatçı (2015), shah (2009), tao (2012), tech archival (2014), trans adriatic pipeline-tap (2015), shimizu, Dejima, and toyosada (2012), veera, nirmalakhandan, and Deng (2010), veera (2011), venkatesh (2011), vince (2007), Wang et al. (2012), Water in the West (2013), Water resources policy Division, land and Water Bureau (2006), World Health organization and un Icef (2014).
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International Journal of Water Resources Development
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A framework for understanding energy for water
Christopher Napoli & Berenice Garcia-Tellez
To cite this article: Christopher Napoli & Berenice Garcia-Tellez (2016) A framework for
understanding energy for water, International Journal of Water Resources Development, 32:3,
339-361, DOI: 10.1080/07900627.2015.1122579
To link to this article: https://doi.org/10.1080/07900627.2015.1122579
© 2017 The Author(s). Published by Informa
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INTERNATIONAL JOURNAL OF WATER RESOURCES DEVELOPMENT, 2016
VOL. 32, NO. 3, 339–361
http://dx.doi.org/10.1080/07900627.2015.1122579
A framework for understanding energy for water
Christopher Napoli and Berenice Garcia-Tellez
King Abdullah Petroleum Studies and Research Center, Riyadh, Saudi Arabia
Introduction
Oceans cover 71% of the earth’s surface and represent over 96% of the world’s total water
resources. Of the remaining water, half is frozen in glaciers or ice caps and a quarter is locked
in saline underground aquifers. This leaves less than 1% of the world’s total water resources
available for consumption by life on earth, a small percentage in relative terms, but a gure
representing 10.6 million km3, or 1.5 million m3 per person (own calculations, data from
Gleick, 1993). As the hydrological cycle results in much of the world’s freshwater being recy-
cled after consumption, the current stock of water is more than enough to sustain life on
earth.
While there is enough freshwater on earth, nearly 20% of the world’s population faces
physical water scarcity, a situation in which there is insucient water to meet the demands
of the ecosystem. The United Nations estimates that if population and economic growth
continue to strain the world’s water resources, roughly two-thirds of the world’s population
could be living in water-stressed regions by 2025 (United Nations Department of Economic
& Social Aairs [UNDESA], 2014).
One of the fundamental components in addressing physical water scarcity is energy. This
is because energy is a primary input for moving water from areas of relative abundance to
areas of relative scarcity. For example, in California, water from the abundant north of the
state travels hundreds of kilometres over the eastern Sierra Nevada mountain range in order
to meet demand in Los Angeles, a region of increasing physical water scarcity. The energy
ABSTRACT
This article oers a framework for understanding how energy is used
to meet water demand in countries. Specically, the relationships
between energy use and water scarcity, the location of renewable
water resources, and aggregate water demand are explored. The
article also examines how policy options such as water price reforms,
agriculture subsidies and crop elimination may inuence the energy
use and energy intensity of water withdrawals. Conclusions suggest
that while policy options exist, certain uncontrollable factors such
as severe water scarcity or substantial freshwater abundance limit
the ability of some countries to signicantly improve the aggregate
energy eciency of water provision.
© 2016 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/
licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
KEYWORDS
Water-energy nexus;
water scarcity; renewable
resources; price reforms;
factor productivity
ARTICLE HISTORY
Received 1 June 2015
Accepted 17 November 2015
CONTACT Christopher Napoli Christopher.napoli@kapsarc.org
OPEN ACCESS
340 C. NAPOLI AND B. GARCIATELLEZ
required to transport water this distance is estimated to be 1.6 kWh/m3, or three times the
energy required to extract and treat water withdrawn from sources in Los Angeles (Wilkinson,
2000). The need for energy-intensive interbasin water transfers is expected to increase as
the population and economy of the city grow.
In Jordan, a severely water-scarce country, a dierent sort of water transport occurs.
Groundwater from aquifers located more than 1 km below the earth’s surface is extracted
for use by municipalities and agriculture. This extraction comes at a tremendous energy cost.
Hayek (2014) estimates that the average energy required to extract groundwater in Jordan
is roughly 1.2 kWh/m3, or nine times the energy required to withdraw groundwater in the
Netherlands, a country also reliant on groundwater, but with much shallower bores (Imperial
Irrigation District, 2015). The case of Jordan is important because the country imports 97%
of its energy from neighbouring countries, and these energy supplies are largely in the form
of non-renewable fossil fuels that can experience large uctuations in price (Talozi, Al Sakaji,
& Altz-Stamm, 2015).
In rare cases, such as Spain, Australia and the Gulf region, seawater is desalinated, as nei-
ther interbasin transfers nor deep aquifer extraction are sucient to meet water demand.
Desalination represents the most energy-intensive option for meeting water demand, and
often entails signicant nancial and environmental costs.
Exploring the relationship between energy and water demand is important for two rea-
sons. First, a signicant amount of energy is used for direct water services. For example,
Sanders and Webber (2012) have estimated that 8.3% of 2010 annual primary energy con-
sumption in the United States was used for the heating, chilling, treating, pressurizing and
pumping of water by the municipal, industrial and agricultural sectors. Thus, water con-
servation can have a direct eect on energy use, which can help improve energy security
and climate change objectives, particularly when fossil fuels are used as the energy source.
Second, while water and energy are inextricably linked, they are typically governed in
silos, which can lead to policy fragmentation and a misalignment of incentives. In general,
the energy sector considers water only as it relates to hydropower and water requirements
for thermal power plants. Similarly, water planners are typically more concerned with supply
augmentation and management, as opposed to energy issues (Malik, 2002). Improving coor-
dination of the management of water and energy resources can increase eciency in both
areas. For example, Kumar, Scott, and Singh (2013) have shown that power tari reform that
includes pro rata pricing and higher unit rates for electricity would likely lead to improved
eciency and sustainability of groundwater use by farmers in India. This is an important
consideration given that in 2010 India extracted 684km3 of water for agriculture, a gure
representing 90% of total extractions (http://www.fao.org/nr/water/aquastat/data/query/).
This article oers a framework for understanding how energy is used to meet water
demand in both water-scarce and water-abundant countries. Specically, the supply and
demand of water, and the energy required to withdraw that water, are disaggregated: supply
is disaggregated by source and treatment process, while demand is disaggregated by user.
This approach helps policy makers understand the ways decisions in one domain can aect
the other, thus building the case for more integrated management of the water–energy
nexus. Through a detailed examination of how energy is used for water supply, and how
water is used in the economy, the framework also provides policy makers with a tool for
assessing the possibilities (and limits) of eciency improvements in both domains.
INTERNATIONAL JOURNAL OF WATER RESOURCES DEVELOPMENT 341
The article’s conclusions are threefold. First, energy use for water is a function of not only
water scarcity, but also the location of renewable water resources: countries with abundant
renewable water resources that are located in deep aquifers, or far from demand centres, may
still require substantial energy resources to meet water demand. Second, while economic
solutions for managing water resources exist, they can be politically sensitive, and therefore
dicult to implement. This often results in the overuse of water, which can lead to increases in
both aggregate energy use and overall energy intensity of water extraction. Last, while some
countries can reduce the energy used for water by eliminating water-intensive agricultural
crops, certain uncontrollable factors, such as severe water scarcity or high water abundance,
reduce the ecacy of this option. By disaggregating and exploring how supply and demand
for water can aect energy use, this article oers a theoretical framework through which
to examine the case studies on managing energy for water presented in this special issue.
The supply of water: implications for energy
As described in Figure 1, water can come from both conventional and unconventional
sources. Conventional sources refers to surface water, groundwater and rainwater, all of which
may be treated and then consumed, or sent directly from the source to the nal consumer.
Unconventional sources refers to seawater, brackish water, brine and wastewater, which must
be puried by advanced treatment technologies prior to consumption.
The energy required to meet water demand is dependent on the type of water used,
whether it is treated, and the technology used for treatment. In almost all cases, water used
for agriculture is untreated, and thus consumes the least energy. For example, rainwater con-
sumed directly by agriculture incurs eectively no energy footprint; and untreated surface
water requires only minimal energy for extraction. As farmers begin to extract water from
underground bores or use desalinated water, energy requirements increase.
Water extracted for municipal and industrial use is typically puried prior to consumption.
This can increase energy requirements. Surface water is often contaminated and must be
pumped through numerous lters and disinfected with chlorine and other chemicals before
Figure 1.Sources and uses of water.
342 C. NAPOLI AND B. GARCIATELLEZ
being distributed to the water grid. Groundwater, in contrast, is typically cleaner, and does
not require much treatment aside from the addition of chlorine and other purifying chem-
icals. As a result, most of the energy required to withdraw and purify groundwater is used
for extraction (Burton, 1996; Copeland, 2014; Plappally & Lienhard, 2012).
The energy required for unconventional water withdrawals is a function of three factors:
the type of water withdrawn; the quantity of water withdrawn; and the desalination tech-
nology used. Two primary types of desalination technologies exist: thermal and membrane.
Thermal desalination is a process in which saline water is vaporized, thus separating pure
water from any salts, minerals and other contaminants (Tonner, 2008). Membrane desali-
nation is a process whereby saline water is passed through one or more semipermeable
membranes. The membranes separate pure water from salts and other impurities. The energy
required for thermal desalination processes such as multistage ash distillation (MSF) and
multiple-eect distillation (MED) is higher, and is independent of the salinity or the source
of water. In contrast, the energy required for membrane technology, such as reverse osmosis
(RO) and electrodialysis (ED), is generally less, and varies with the salinity of water: the more
saline the water, the more energy-intensive the extraction and treatment. In addition to
the specic technology used, other factors will aect the energy required for desalination,
including output capacity of the plant, thermal design, membrane type (for membrane
technologies), eciency of the plant, and system conguration. The latter is important to
consider for dual-purpose plants (i.e. plants designed for power and water production).
While global online seawater desalination capacity increased signicantly between 2000
and 2014, from 0.72km3 to 13.73km3 (Global Water Intelligence, 2015), given its high capital
and energy costs, the technology contributes only a small fraction to overall water supplied.
Figure 2 describes how energy use increases with dierent water sources and extrac-
tion technologies. With the exception of rainfall, untreated surface water requires the least
energy for extraction, with the variance in energy required due primarily to the varying
eciency of pumps for extraction. In emerging economies, where pumps are often less
ecient and energy costs are lower, energy intensity is generally higher. The gure also
shows that while some water sources are more energy-intensive than others, each source
has a large range of possible energy intensities. For example, while it is generally assumed
that treated wastewater is more energy-intensive than groundwater extraction, this may not
be the case when groundwater bores are deep and pumps are inecient. This is an impor-
tant consideration in water-scarce countries that must rely on deep groundwater aquifers.
Wastewater treatment may also oer a less energy-intensive alternative to desalination. In
Saudi Arabia, a severely water-scarce country, the government has begun to encourage the
reuse of wastewater, and plans have been put in place to expand wastewater collection and
treatment systems to cover about 60% of urban areas by 2014 – up from 42% in 2010 (Ouda,
2014). To date, much of the recycled water has been used for urban-area landscaping and,
to a lesser extent, crop irrigation (Ouda, 2014). It is hoped that wastewater will help alleviate
stress on non-renewable aquifers through less energy-intensive, cheaper means than can
be oered by desalination. The case of Saudi Arabia shows that when countries understand
the economic and energy implications of dierent water sources, it is feasible for strategies
to be implemented that minimize these costs.
An important source of water that is not considered in Figure 2 is water transported over
long distances. Lack of data and extreme dierences in the characteristics of water transport
networks make it dicult to establish useful energy-intensity ranges for water transport at
INTERNATIONAL JOURNAL OF WATER RESOURCES DEVELOPMENT 343
the national level. For example, when water transport systems are gravity-fed, such as the All-
American Canal, located in Southern California adjacent to the Mexican border, energy can
be produced from hydroelectric power plants. The All-American Canal is used to transport
3.8km3 of water 82 miles from the Colorado River to the Imperial Valley (Imperial Irrigation
District, 2015), and the process generates more than 253 million kWh of electricity on an
annual basis. In contrast, the proposed Ebro project in Spain that sought to transfer 860
GL/y of water from the Ebro River a distance of 745km to the south of the country was
predicted to require roughly 4 kWh/m3 (Marcuello, Capilla, Murillo, Barcones, & Meyer, 2003;
Plappally & Lienhard, 2012). The Ebro water transfer project was cancelled in 2004 due to
social, environmental and economic concerns. Studies suggested that the project would
have led to the disappearance of the Ebro Delta, an important wetland in Spain, and that
the economic costs would have been higher than initial government estimates (World Wide
Fund for Nature [WWF], 2003).
According to Plappally and Lienhard (2012), energy intensity of water transport systems
is location-specic, and dependent on factors such as pipeline grade, the soil’s seepage
or percolation properties, solar radiation and climatic behaviour in a given geographical
Figure 2.Energy required for different types of water. Sources: Al-Karaghouli and Kazmerski (2013),
Abdel-Jawad (2001), Buenomena (2013), Darwish, Al-Najem, and Lior (2009), Drewes (2011), Global
Water Intelligence (2015), Hamed (2004), Hayek (2014), Ludwig (2010), Matar, Murphy, Pierru, and Rioux
(2014), Plappally and Lienhard (2012), Veera (2011), Vieira, Beal, Ghisi, and Stewart (2014). Note: Vapour
compression (VC) desalination is a modified form of the MED process where the evaporation of seawater
is obtained by the application of heat through a mechanical compressor. In this unique process, the
energy requirements are lower than MSF/MED thermal cogeneration technologies, which is why the
‘thermal stand-alone’ technology has lower potential minimum energy requirements. In general, thermal
cogeneration processes are less energy-intensive than thermal stand-alone processes.
344 C. NAPOLI AND B. GARCIATELLEZ
region. Although dicult to generalize, energy for water transport can represent a signif-
icant proportion of the total energy required to meet water demand. For example, Hardy,
Garrido, and Juana (2012) have estimated that 21% of the total energy used to meet water
demand in Spain goes to distribution and water transport. It should be noted that while his-
torically water transport was primarily used to address municipal water-scarcity challenges,
it is increasingly being used for agriculture and industry.
Water scarcity and energy use
The water scarcity of a country is traditionally measured as the ratio of its water withdrawals
to total renewable water resources (Brown & Matlock, 2011). If a country withdraws less than
20% of its total renewable water resources it is considered water-abundant. When a country
withdraws between 20% and 40% of total renewable water resources it is considered water-
scarce; and when the ratio exceeds 40%, the country is considered severely water-scarce.
Figure 3 estimates the relationship between water scarcity and the aggregate energy
intensity required to provide a cubic metre of water in a sample of countries. Water-scarcity
ratios were obtained from Aquastat (http://www.fao.org/nr/water/aquastat/data/query/)
and national accounts. Energy data were compiled by estimating three sources: untreated
surface and groundwater, treated surface and groundwater, and desalinated unconventional
water. Given data limitations for numerous countries, energy for interbasin water transport
and wastewater treatment were not included in the calculations, and so the energy intensity
is probably underestimated, particularly in water-scarce regions where large interbasin water
transfers occur or where substantial wastewater treatment occurs.
The energy required to extract untreated surface water was estimated to be 0.023 kWh/m3
for OECD countries and 0.034 kWh/m
3
for non-OECD countries. These values were calculated
based on a theoretical lift parameter (l, 2.73 kWh to lift 1000m3 a height of 1 m), a hydraulic
head (h) of 5 m, and a pump eciency (ε) of 40% for non-OECD countries and 60% for OECD
countries, and described in the equation below.
This equation has been used to estimate energy for water extraction in a number of stud-
ies, notably that of Nelson et al. (2008). While the eciencies of pumps can vary within
and between countries, particularly when both electrical and diesel pumps are used, the
assumptions and results obtained are in line with case studies from both developed and
emerging economies (Abadia, Rocamora, Ruiz, & Puerto, 2008; Japikse, Marscher, & Furst,
1997; Moreno, Carrion, Planells, Ortega, & Tarjuelo, 2007; Shah, 2009). Energy for untreated
groundwater was estimated in the same manner, with groundwater depths coming from a
variety of government gures and academic studies. Energy for treated water in countries
came from academic studies and reports from utilities, while energy for desalinated water
was derived from numerous academic and government sources (see sources section of
Figures 3 and 6). Despite the use of aggregated data, sensitivity analysis in which pump
eciencies and energy requirements for water treatment were varied under multiple sce-
narios did not greatly alter the aggregate relationships between countries. Given this, one
can assume that the analysis above oers a reasonable estimate of the relationship between
water scarcity and energy intensity for water in the sample of countries.
e
GW =
l
h
𝜀
INTERNATIONAL JOURNAL OF WATER RESOURCES DEVELOPMENT 345
Figure 3.Energy intensity of water (extraction and treatment) and water scarcity in a sample of countries.
Sources: Abderrahman (2001), Agenda 21 Della Terra d’Arneo (n.d), Al-Karaghouli & Kazmerski (2013),
Al-Mashaikhi (2011), Al-Mooji, Hofstetter, & Renck (2013), Abdel-Jawad (2001), Aqualogy (http://www.
aqualogy.net), Aquastat (http://www.fao.org/nr/water/aquastat/data/query/), Association of Private
Water Operators (2013), Australian Bureau of Statistics (2014), Basharat (2012), British Geological Survey
(2015), Buenomena (2013), Bundesanstalt für Geowissenschaften und Rohstoffe (2015), Burton (1996),
Campanelli, Foladori, and Vaccari (2013), Chan (2013), China Urban Water Association (2012), Chudaeva
et al. (2008), CONAGUA (2014), CONUEE (2011), Copeland (2014), Darwish et al. (2009), Department for
Environmental, Food and Rural Affairs (2008), Department of Environment, Water and Natural Resources
(2014), Dimakis, Colleuille, & Wong (2005), Drewes (2011), ECRA (2011), El Tahlawi, Farrag, and Ahmed
(2008), Encyclopedia of Desalination and Water Resources (2014), Entidade Reguladora dos Serviços de
Águas e Resíduos [ERSAR], (2012), Environmental Agency Abu Dhabi (2014), European Benchmarking
Cooperation (2014), European Environment Agency (2014), Frijns, Mulder, and Roorda (2008), Gaut (2010),
Global Water Intelligence (2015), Godskesen, Hauschild, Rygaard, Zambrano, and Albrechtsen (2013),
Hadian, Mardiana, Abdurahman, and Iman (2006), Hamed (2004), Hardy et al. (2012), Hayek (2014),
Hernández-Mora, Martinez-Corona, Llamas-Madurga, and Custodio-Gimena (2010), Imperial Irrigation
District (2015), International Groundwater Resources Assessment Centre [IGRAC] (https://ggmn.unigrac.
org), Japan Waterworks Association (2014), Lemos, Dias, Gabarrell, and Arroja (2013), Ludwig (2011),
Karimov et al. (2015), Kenway et al. (2008), Kumar (2013), Kwanyuen, Mainuddin, and Cherdchanpipat
(2003), Li, Liu, Zheng, Han, and Hoff (2015), Maas (2009), MacHarg and McClellan (2004), Matar et al. (2014),
McLay (2005), McMahon and Price (2011), Margat and van der Gun (2013), Ministry of Water & Electricity
(2010), Ministry of Water and Irrigation (2015), Nelson et al. (2008), Natural Resources Canada Database
(2014), Papapetrou, Wieghaus, & Biercamp (2010), Pearce (2007), Peng (2014), Plappally and Lienhard
(2012), Portela and Cohim (2011), Qatar General Electricity and Water Corporation (2014), Queensland
Department of Natural Resources and Mines (2014), Raucher et al. (2010), Reboucas (1999), Renzoni and
Germanin (2007), Saatçı (2015), Shah (2009), Tao (2012), Tech Archival (2014), Trans Adriatic Pipeline-TAP
(2015), Shimizu, Dejima, and Toyosada (2012), Veera, Nirmalakhandan, and Deng (2010), Veera (2011),
Venkatesh (2011), Vince (2007), Wang et al. (2012), Water in the West (2013), Water Resources Policy
Division, Land and Water Bureau (2006), World Health Organization and UN ICEF (2014).
346 C. NAPOLI AND B. GARCIATELLEZ
It is often assumed that energy intensity and water scarcity are positively correlated. As
Figure 3 shows, this is true when the severely water-scarce countries of the Gulf region are
considered. The Gulf countries contain almost no surface water, and so they rely on desali-
nation and deep underground fossil aquifers in order to meet water demand. For example,
the United Arab Emirates obtains 24% of its water from desalination, while 70% comes from
fossil aquifers, and only 6% from surface water. Fossil aquifers take thousands of years to
form, and when water is withdrawn from them, the total water available for future gener-
ations decreases. The Environment Agency of Abu Dhabi estimates that water levels in the
agricultural region of Al Khazna fell from 56 m to 96 m between 1999 and January 2014,
while water levels just north, in Sweihan, fell from 46 m to 104 m between 1998 and 2013
(Malek, 2015). The non-renewable nature of these aquifers causes them to fall when water
is extracted; and as water levels drop, the energy costs for extraction rise.
When excluding the Gulf region, however, there is eectively no correlation between the
energy intensity of water extraction and water scarcity. For example, the severely water-
scarce countries of Pakistan and Egypt use less energy per unit of water extracted than
Portugal, a water-abundant country. The primary dierences between these countries
are twofold. First, while Portugal enjoys abundant renewable freshwater resources, these
resources exist as groundwater, which, as stated, requires more energy for extraction com-
pared to surface water. In Portugal, 74% of the total water supply comes from underground
aquifers. In contrast, Egypt obtains 89% of its water from the surface, primarily the Nile Delta,
while Pakistan obtains 65% of its water from lakes and rivers. Thus, while the total renewable
water resources in Egypt and Pakistan are being exhausted more quickly than in Portugal,
the energy requirements for this extraction are lower, as the water is being extracted from
more accessible sources.
Second, water scarcity estimated at the national level can be misleading. This is because
regional dierences within a country can have a profound impact on actual water resources
readily available to the populace. Portugal is not considered a water-scarce country because
of the abundant water resources in the country’s north. Much of the country’s population and
agricultural activity, however, are located south of the city of Porto, where water resources
are scarcer, and so groundwater from deeper sources must be withdrawn. In Egypt and
Pakistan, while renewable water resources are scarcer at the national level, they are much
more accessible to the population, and thus require less energy. The situation is similar
in Australia, a country considered water-abundant due to the extensive water resources
located in the tropical north, despite the fact that an estimated 65% of the population live
in water-scarce regions (own calculations, data from Australian Bureau of Statistics, 2015;
Chartres & Williams, 2006; The Economist, 2007; World Bank, 2015). While imperfect, national
water-scarcity calculations are still useful as they oer a theoretical indication of the water
resources that can be mobilized by the state for extraction and consumption.
An additional factor that can aect the relationship between water scarcity and energy
intensity is total water withdrawals. Consider the cases of the United Kingdom and Spain.
The two countries have similar energy intensities despite the fact that Spain is a more water-
scarce country, uses far more desalination, has deeper average groundwater bores, and
extracts more than twice the groundwater (roughly 5.7 km3 compared to 2.16 km3; http://
www.fao.org/nr/water/aquastat/data/query/). The similarities in energy intensity are due to
the way water is used in agriculture. In the UK, the total value added by agriculture in 2013
was only USD 12 billion, or 0.5% of the nation’s total GDP (in constant 2005 USD; United
INTERNATIONAL JOURNAL OF WATER RESOURCES DEVELOPMENT 347
Nations Statistics Division, 2015). The UK enjoys ample rainfall, and so it only extracts roughly
1.3km3 of water to achieve that agriculture production. Spain is a far dryer country, but in
2013 its agriculture sector contributed 3% to the GDP, a gure representing USD 35 billion.
Because of the sector’s size and the country’s climate, Spain must extract 20km3 of water for
agriculture. While Spain extracts far more water for agriculture than the UK, over 79% of this
water comes from the surface. This signicantly reduces the average energy intensity required
to meet water demand. This result, however, is somewhat misleading because Spain uses far
more total energy to meet water demand given the higher overall levels of water extraction.
This section has assessed the supply of water resources. It has demonstrated that water
comes from a number of dierent sources that have varying energy requirements. In theory,
water-abundant countries will have lower energy intensities for water withdrawals. In prac-
tice, this relationship is complicated by factors such as regional water scarcity, the location
of total renewable water resources, and total water use. The analysis also suggests that as
countries exhaust easily obtainable water resources they are likely to move to more expen-
sive, and energy-intensive, water resources. This phenomenon is prevalent in the Gulf region.
It should be noted that energy-intensive water sources are, in general, also the most costly,
and so as countries move up the marginal cost of energy curve, the total costs of water often
increase (Figure 2).
The extent to which countries must shift to more energy-intensive water resources is
a function of not only water supply but also how water is used by the population and the
economy. The demand for water is addressed in the following section.
The determinants of water demand
Only a small percentage of water extracted is consumed directly by the population. Globally,
roughly 70% of all water withdrawn is used for agriculture, while 19% is an input for industrial
processes (http://www.fao.org/nr/water/aquastat/data/query/). Of the remaining 11% of
water allocated to municipalities, much is used either by rms (local companies connected to
the municipal grid) or for irrigation in residential communities. Given that so much extracted
water is used as an input for production, it is appropriate to consider the resource from the
perspective of production theory, whereby output (Y) will be some function of a combination
of inputs, such as capital (K), labour (L), land (H) and water (W):
The relative contribution of each factor of production to output is determined by compar-
ative productivity. Productivity is dened as output (typically represented in physical or
monetary terms) per unit input (represented in terms of monetary costs or input units). In
the short run, it is almost always possible to increase the productivity of an individual input.
Without technological innovation, however, this increase will come at the expense of the pro-
ductivity of other factors. For example, a farmer could reduce the amount of extracted water
required to produce crops (i.e. increase water productivity) by investing in drip-irrigation
technologies (i.e. increasing capital expenditures, and thus decreasing capital productivity)
or employing more labour to irrigate plants directly by hand (i.e. increasing labour expendi-
tures, and thus decreasing labour productivity). A farmer will only choose to substitute water
for capital or labour if the cost savings from using less water are greater than the increased
expenditures from employing more capital or labour. In cases where the costs of installing
Y=F(K,L,H,W)
348 C. NAPOLI AND B. GARCIATELLEZ
drip irrigation or increasing labour use are higher than the savings from using less water, the
investment will not make economic sense, as it will increase the total costs of production.
It should be noted that, because energy can represent up to 25% of groundwater system
production costs (Dhuyvetter, O’Brien, Haag, & Holman, 2014; Zilberman, Sproul, Rajagopal,
Sexton, & Hellegers, 2008), the cost of water use for agriculture may vary considerably with
uctuations in energy costs: the higher the energy costs, the more incentive there may be
for a farmer to invest in water savings.
The amount of water used for production is a function of the relational costs between
water and other factors of production. Water is used excessively in production when it is
valued less than substitute inputs. Malik (2002) has argued that “inecient use of both water
and electricity in large part is also the result of non-metering of the consumption and the
non-remunerative tari structures for these services”. The eects of this ineciency are not
restricted to producers, but can also aect how embodied water is consumed. Allan, Keulertz,
and Woertz (2015) have noted that the true values of water and energy are not reected
in the prices of food and manufactured commodities paid by consumers in private-sector
markets. As a result, the quantity demanded of these products, and thus the total water and
energy used in their production, can rise.
If policy makers seek to change the relative contributions of each input to production,
there are eectively two options: decrease the costs of substitute inputs (such as labour
Figure 4.Potential effects of capital and labour subsidies on water consumption. Adapted from Sorrell
(2014).
INTERNATIONAL JOURNAL OF WATER RESOURCES DEVELOPMENT 349
and capital) or increase the cost of water. The rst option is achieved through subsidies. For
example, farmers could be oered more ecient drip-irrigation technologies at subsidized
prices, or be oered tax rebates for employing more labour. The second option is achieved
through increasing the price of water, either by introducing a tax or increasing the prices
of water inputs, namely energy, which, as stated, is often the largest single cost for water
provision.
Both options have drawbacks. Figure 4 shows the potential eects of a capital or labour
subsidy on water consumption. In the gure, vector C represents the total costs of agricultural
production while isoquant Y, which is assumed to be homothetic, represents the possible
mix of water W and the nest, N, of land, labour and capital, for production. In the scenario,
prior to the introduction of the subsidy the point of tangency is {Y0,C0}. This intersection
represents the chosen mix of factors of production given cost constraints. A subsidy on land,
labour, and/or capital decreases the total costs of N, which leads to an outward shift of the
total cost curve, from C0 to C1. This movement has two eects.
First, there is an overall increase in production, as cheaper inputs allow for increased pro-
duction for the same costs. This increase in production leads to a shift in water use from W0
to W1. Second, there is a substitution of W for N, which leads to a movement upward along
the Y isoquant, from W1 to WS, where S represents subsidy. The net eect of the subsidy on
aggregate water consumption will depend on the relationship between the substitution
and cost eects. In instances where the cost eect is greater than the substitution eect
(W1W0>W1WS), the subsidy will lead to an increase in aggregate water consumption,
from W0 to WS, as demonstrated in Figure 4.
In practice, this eect could be described as follows. When labour or capital is subsidized,
the total costs of production are reduced. While this may reduce water usage per unit of
output, it may also increase the protability of the industry, thus encouraging more pro-
duction (either by incumbents or new entrants), and increasing aggregate water use. Also,
if producers are operating in a competitive market, cost reductions may cause end prices
for consumers to decrease, which can increase quantity demanded. The lack of aggregate
savings from technologies meant to raise eciency is known as Jevons’ paradox (Alcott,
2005), or the rebound eect. Empirical studies suggest that irrigation modernization may
lead to a rebound eect that negates eorts to improve water productivity. Pfeier and Lin
(2014) found that irrigation eciency in western Kansas from 1995 to 2005 led to increases
in groundwater extraction of over 100%. The results were due primarily to switching to more
protable, but also more water-intensive, crops. Similarly, Ward and Pulido-Velázquez (2008)
showed that water conservation subsidies in the Rio Grande Basin have not reduced aggre-
gate water use, as farmers have simply increased yields. Because energy use is directly related
to water use, when water consumption increases so does aggregate energy consumption.
The second option, increasing the price of water, oers a better economic solution for
improving water productivity and decreasing energy consumption. As Figure 5 shows, a
water tax leads to increased costs for water, causing an inward shift from C0 to C1. This shift
also has two eects. First, lower production reduces total water use, from W0 to W1. Second,
higher water costs make other factors more attractive, leading to a substitution eect equal
to W1WT, where T represents tax. Thus, the total reduction of water resulting from the tax
is W0WT.
In practice, the eect of a tax could be described as follows. An increase in the price of
water will raise the total costs of production, which will result in reduced production and/
350 C. NAPOLI AND B. GARCIATELLEZ
or lower quantity demanded of products. In principle, this reduction in water use will lead
to lower energy consumption for the provision of that water. While a tax may be an eco-
nomically favourable solution, it is rarely implemented, as it is politically sensitive given the
reductions it would entail in rm protability as well as consumer welfare.
It should be noted that the logic above also applies to households using municipal water
supplies. Households could be incentivized to reduce water use (for example by adopting
low-ow faucets and showerheads) either by increasing the price of water or by subsidizing
the prices of water-conserving technologies. The eects of household water reductions on
energy are signicant. This is because the energy savings related to the reduction of water
use by household items such as washing machines, dishwashers and showers, although often
overlooked, can be as high as 11.2 times the energy used to deliver water services (Kenway et
al., 2008). As with water use for production, however, subsidies can lead to a rebound eect
(i.e. increases in aggregate water use), while taxes can lead to cost increases (i.e. a decrease
in welfare). It should be noted that even though taxes may be preferable, nding the correct
level of tax can be dicult. Easter and Liu (2007) have suggested that one reason private
and social costs of water are not included in taris is that they are dicult to estimate and
may be beyond the knowledge of many countries. The authors argue for additional reforms
to complement increases in water taris. For example, volumetric pricing, as opposed to
simply charging farmers per hectare irrigated, could improve the eciency of water used.
Likewise, water quotas can be used to force water use reductions.
The analysis above suggests that while economic solutions for managing water resources
exist, they can be politically sensitive, and therefore dicult to implement. This often results
in overuse of water by households, industry and agriculture. Overuse has two implications for
Figure 5.Potential effects of a water tax on water consumption. Adapted from Sorrell (2014).
INTERNATIONAL JOURNAL OF WATER RESOURCES DEVELOPMENT 351
energy. First, it increases overall energy consumption, as energy use is a function of total water
withdrawn. Second, and perhaps more importantly, high water use can necessitate a movement
to more energy-intensive water sources, thus increasing the average energy required to meet
water demand. This is exemplied in Figure 6. The gure shows the per capita energy required to
meet water demand in a sample of countries under two scenarios. The rst scenario is a baseline,
showing per capita energy for water under current consumption practices. The second scenario
shows how this per capita energy use could change if the three most water-consuming crops
in each country were removed from production. The top of the dotted bar (referred to as the
Crop Reduction Scenario) assumes a reduction in the crop’s actual water source, while the top
of the solid bar (referred to as the Crop Reduction + Zero Desalination Scenario) assumes that
water reductions occur in the most costly and energy-intensive sources, such as desalination
and deep groundwater withdrawals. Any level within the dotted area represents some com-
bination of a reduction in actual water sources and the most energy-intensive water sources.
Figure 6 suggests that crop elimination has the potential to dramatically reduce energy
intensity for water extraction in some countries. For example, in 2010 Saudi Arabia used 2301
kWh per capita to extract and treat water for municipalities, industry and agriculture. If the
country’s three most water-intensive crops – alfalfa, dates and wheat – were eliminated in
that year, total freshwater withdrawals would have been reduced from 25km3 to 15km3. If
reductions occurred from each crop’s actual source (typically deep groundwater aquifers), per
capita energy consumption for water would have been reduced to 2094 kWh. Saudi Arabia,
however, desalinated roughly 1.3km3 of water in 2010. Eliminating the three crops would
reduce the need for this expensive and energy-intensive desalination, as the desalinated
water could be replaced in part or in full by conventional water, eectively allowing the coun-
try to move down the marginal cost of energy curve. If all of the country’s desalinated water
were replaced by conventional groundwater, this would reduce the average energy required
to meet water demand by 87%. It should be noted that the water reductions from eliminating
these crops would decrease total freshwater consumption by 41%, which would still result
in Saudi Arabia being a severely water-scarce country, but non-renewable water resources
would be depleted at a much lower pace. The situation is similar in Oman. Eliminating the
three most water-intensive crops in 2010 would have signicantly reduced the average
energy intensity of water extraction, as well as reducing water scarcity by 53%. As with a
water tax, eliminating crops is a politically sensitive topic, as some countries consider this a
surrendering of food security. Despite this, recent developments suggest that it is possible.
The government of Saudi Arabia has mandated the elimination of wheat production by
2016, and Almarai, the country’s largest dairy producer, is employing a strategy to import
all of the alfalfa it uses as fodder (Almarai, 2014). In 2008, Almarai used roughly 400,000 tons
of domestically produced alfalfa as fodder (Almarai, 2009). This gure represented 20% of
the total fodder used by the company that year, and roughly 16% of the total alfalfa that
was produced in Saudi Arabia. Eliminating this alfalfa would reduce water consumption
by 0.9km3. If similar commitments were made by other agriculture producers that rely on
alfalfa as feed, and domestic alfalfa production were eliminated, this would reduce water
consumption by an estimated 6km3 (FAOStat, http://faostat3.fao.org/home/E; Ministry of
Agriculture, 2014; Multsch, Al-Rumaikhani, Frede, & Breuer, 2013). While dates are more
politically and culturally sensitive, the elimination of both fodder and wheat would reduce
water consumption by 7.3km3 (FAOStat, 2015; Ministry of Agriculture, 2014; Multsch et al.,
2013), which is far more than the current production of desalinated water. These types of
352 C. NAPOLI AND B. GARCIATELLEZ
Figure 6.Energy for water per capita, baseline and crop elimination. Sources: Abderrahman (2001),
Agenda 21 Della Terra d’Arneo (n.d), Al-Karaghouli & Kazmerski (2013), Al-Mashaikhi (2011), Al-Mooji,
Hofstetter, & Renck (2013), Abdel-Jawad (2001), Aqualogy (http://www.aqualogy.net), Aquastat (http://
www.fao.org/nr/water/aquastat/data/query/), Association of Private Water Operators (n.d), Australian
Bureau of Statistics (2014), Basharat (2012), British Geological Survey (2015), Buenomena (2013),
Bundesanstalt für Geowissenschaften und Rohstoffe (2015), Burton (1996), Campanelli et al. (2013),
Chan (2013), Chudaeva et al. (2008), CONAGUA (2014), CONUEE (2011), Copeland (2014), Darwish
et al. (2009), Department for Environmental, Food and Rural Affairs (2008), Department of Environment,
Water and Natural Resources (2014), Dimakis, Colleuille, & Wong (2005), Drewes (2011), ECRA (2011), El
Tahlawi et al. (2008), Encyclopedia of Desalination and Water Resources (2014), Environmental Agency
Abu Dhabi (2014), European Benchmarking Cooperation (2014), European Environment Agency (2014),
Frijns et al. (2008), Gaut (2010), Global Water Intelligence (2015), Godskesen et al. (2013), Hadian et al.
(2006), Hamed (2004), Hardy et al. (2012), Hayek (2014), Hernández-Mora et al. (2010), Imperial Irrigation
District (2015), International Groundwater Resources Assessment Centre [IGRAC] (https://ggmn.unigrac.
org), Japan Waterworks Association (2014), Lemos et al. (2013), Ludwig (2011), Karimov et al. (2015),
Kenway et al. (2008), Kumar (2013), Kwanyuen et al. (2003), Li et al. (2015), Maas (2009), MacHarg and
McClellan (2004), Matar et al. (2014), McLay (2005), McMahon and Price (2011), Margat and van der Gun
(2013), Ministry of Water & Electricity (2010), Nelson et al. (2008), Natural Resources Canada Database
(2014), Papapetrou, Wieghaus, & Biercamp (2010), Pearce (2007), Peng (2014), Plappally and Lienhard
(2012), Portela and Cohim (2011), Qatar General Electricity and Water Corporation (2014), Queensland
Department of Natural Resources and Mines (2014), Raucher et al. (2010), Reboucas (1999), Renzoni and
Germanin (2007), Saatçı (2015), Shah (2009), Tao (2012), Tech Archival (2014), Trans Adriatic Pipeline-
TAP (2015), Shimizu et al. (2012), Veera et al. (2010), Veera (2011), Venkatesh (2011), Vince (2007), Wang
et al. (2012), Water in the West (2013), Water Resources Policy Division, Land and Water Bureau (2006),
World Health Organization and UNICEF (2014). Note: Energy values from KAPSARC analysis on energy
for surface water abstraction, groundwater abstraction and desalination. Crop water use data from the
Water Footprint Network (average values between 1996 and 2005). Crop production data from FAOSTAT
for the year 2011 (http://faostat3.fao.org/home/E).
INTERNATIONAL JOURNAL OF WATER RESOURCES DEVELOPMENT 353
initiatives are necessary to help the country reach its goal of reducing water withdrawals
by 30% by 2030, and if coupled with reductions in energy-intensive water supplies, could
also lead to energy reductions.
In addition to estimating the potential benets from crop elimination in some coun-
tries, there are two other important ndings from the gure. First, in the four other Gulf
Cooperation Council (GCC) countries, Kuwait, the United Arab Emirates, Qatar and Bahrain,
eliminating water-intensive crops has eectively no impact on average energy used for
water, as no water-intensive crops are grown on a large scale in these countries. For energy
intensity reductions to occur, crop elimination must be coupled with a movement away from
desalination towards conventional water. This strategy is unfavourable, however, because a
shift away from desalinated water would increase aggregate groundwater use, which would
raise the overall water scarcity of the countries. For these severely water-scarce countries,
where desalination is required, two options exist for reducing energy use: reducing municipal
water consumption; and/or adopting more energy-ecient desalination technologies (i.e. a
movement from thermal technologies to membrane technologies). Second, some countries,
like Mexico, Canada and Norway, would enjoy only minimal reductions in average energy
consumption with the elimination of water-intensive crops. This is because most crops in
these countries rely on rainwater, and so energy use for extracted water is marginal. For
example, over 99% of the water used to grow wheat in Canada and Norway comes from
rainfall (own calculations, data from Mekonnen & Hoekstra, 2011). In cases where crop elim-
ination does not aect energy intensity, countries may consider reducing municipal water
consumption, or adopting more ecient pumps for extraction.
Virtual trade in water: implications for water and energy savings
Allan (1998) has dened the virtual-water content of a commodity, good or service as the
volume of water used in its production. The trade in virtual water, therefore, represents the
amount of water embedded in products traded internationally. Using this framework, Allan’s
work has explored how food trade may aect the water economies and policies in water-
scarce countries (Allan, 2003). He has argued that importing water-intensive crops oers a
policy option for countries with water decits, which may even be particularly valuable for
preventing ‘hydropolitics’ from sparking full-scale conicts (Allan, 2002).
Building on Allan’s insights, Hoekstra and Hung (2002) examined the volume of virtual
water trade ows between countries, putting national water trade balances in the context of
domestic water requirements and resources. This work oers an empirical assessment of the
way countries are water-dependent on others. More recent work in this area has suggested
that “about one-fth of both global cropland and agricultural water use is allocated to the
production of agricultural commodities consumed abroad” (Hoekstra & Mekonnen, 2012,
quoted in MacDonald et al., 2015).
The high potential for virtual water trade to improve the sustainability of water resources
in water-scarce countries should be complemented with an analysis of energy savings. As
shown in Figure 6, crop elimination, which is eectively a substitution away from domestic
production to imports, could lead to signicant reductions in both total energy use and, in
some cases, the intensity of energy used to meet water demand, both of which would have
positive eects on sustainability and the environment.
354 C. NAPOLI AND B. GARCIATELLEZ
Conclusion
This article oers a framework for evaluating how energy is used to meet water demand.
The supply of and demand for water, and the energy required to withdraw that water, were
disaggregated. The supply analysis demonstrates that water comes from a number of dif-
ferent sources that have varying energy requirements. In theory, water-abundant countries
will have lower energy intensities for water withdrawals. In practice, this relationship is com-
plicated by factors such as regional water scarcity, the location of total renewable water
resources, and total water use. The analysis also suggests that as countries exhaust easily
obtainable water resources they are likely to move to more expensive, and energy-intensive,
water resources. This phenomenon is prevalent in the Gulf region as well as water-scarce
regions in developed countries like Spain, Australia and parts of the United States.
Regarding demand, while economic solutions for managing water resources exist, such
as raising water prices or mandating the elimination of some agriculture crops, they can
be politically sensitive, and therefore dicult to implement. It should be noted that some
countries have made progress in these areas. For example, in the mid-1970s, Denmark expe-
rienced two years of drought, in which city water supplies were virtually exhausted. This
resulted in campaigns to conserve water as well as the introduction of water taxes, which
led to a decrease in aggregate municipal water consumption from 605 million m3 in 1980
to 400 million m3 in 2005 (Geological Survey of Denmark & Greenland, [GEUS], 2006). In
addition, as stated, Saudi Arabia has reduced its wheat production since 2008, and plans
to rely solely on imported wheat by 2016. The decision was made because of the negative
impact domestic wheat production has on water resources. The country is trying to meet
its food security goals through other means, such as the creation of the Saudi Agricultural
and Livestock Investment Co. (SALIC), which has been endowed with USD 800 million to
improve food security in the country through foreign purchases. In 2013, SALIC purchased
40,000 hectares of active farmland in Poland and the Ukraine; and in 2015 the group became
a majority investor in the Canadian Wheat Board. Should these initiatives lower agricultural
water use in the country, there may be potential reductions in the aggregate energy used
for water, as well as average energy intensity for water withdrawals.
The article has suggested that while supply and demand management can reduce the
energy required for water resources, uncontrollable factors may limit the potential ecacy
of certain policy options. For example, in severely water-scarce regions, it is likely that desal-
inated and/or deep aquifer water are necessary components of the water portfolio, and so
these regions will always have a higher overall energy intensity than countries with abundant,
clean surface water. Similarly, it is dicult for water-abundant countries that already rely on
rainwater and surface water to make signicant improvements to energy intensity. In both
cases, focus should be placed on reducing water consumption, as this will lower overall
energy expenditures for water.
Last, it should be noted that the analysis in this article is based on aggregated data from
multiple sources. In some countries, water and energy data are granular and current, while in
others water resources and energy use are based on estimates. Moving forward, it behoves
countries to improve the way water and energy data are collected and published so that
more cross-country research can be done. It is hoped that this special issue contributes, in
part, to this initiative.
INTERNATIONAL JOURNAL OF WATER RESOURCES DEVELOPMENT 355
Acknowledgement
The authors would like to acknowledge the research assistance of Mathieu Carey, intern, King Abdullah
Petroleum Studies and Research Center.
Disclosure statement
No potential conict of interest was reported by the authors.
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... estimate the energy demands in the water and food sectors. Widely reported estimates for energy intensities from(Plappally and Lienhard V 2012;Napoli and Garcia-Tellez 2016) were used in this study with region-specific energy intensities for activities when available(Daccache et al. 2014;Ouda et al. 2016b). Energy for machinery was considered for tractors only since they predominate the machinery use in Egypt. ...
Thesis
Full-text available
Water, food and energy are fundamental for achieving our social, economic and environmental goals. The three domains are inextricably linked and the action in one sector could affect the two other sectors. Achieving the Water, Food and Energy (WFE) nexus balance and improving long-term sustainability through policy interventions is particularly challenging in transboundary river basins because of the dynamic nature and inter-sectoral complexity that may cross borders. Increased pressure from population growth, urbanization and economic growth in riparian countries induce each riparian country to maximise its resources to meet growing water, food and energy demands. Such infrastructure developments and policies in riparian countries could result in basin-wide cooperation or trigger conflicts among the countries. What is more, climate change is likely to exacerbate the risks associated with the hydrologic regime and affect the livelihoods in river basins. The “nexus thinking” shifts the focus from one sector-centric towards multi-centric analytical frameworks to better understand the complexity and improve the management of disparate but interconnected sub-systems. This thesis builds upon the nexus approach and develops a novel systems-based approach to better understand the nexus interactions while considering other related important issues such as long-term uncertainty in river flow regime, socio-economic development, climate change and policy choices in river basins. The framework considers a biophysical water resource model of the river basin and integrated with an agricultural land and crop yield models to account for food production. The energy component includes hydropower generation from the system’s hydropower plants, while energy demand is accounted for energy requirements in water and food sectors. To account for the uncertainty in hydrologic river regime and large variability of the river flows, stochastic simulation is adopted with and without climate change. The population size and Gross Domestic Product (GDP) per capita represent socio-economic characteristics. The water resource model can accommodate future planned infrastructure projects and policies, e.g., improving irrigation efficiency, in the basin. The novel framework is applied for the Nile river basin as a case study. The Nile River basin is a transboundary river basin in East Africa shared by eleven countries and home for about 250 million people. The riparian countries have devised ambitious master plans to utilise potential resources in the basin to meet the growing water, food and energy demands of their populations and sustain their expanding economies. The Nile is vulnerable to climate change that is likely to add further uncertainties to the hydrologic river regime. The – near completion – Grand Ethiopian Renaissance Dam (GERD) is the largest development in the basin and has the potential to deliver regional economic benefits and improve regional cooperation. However, it also has raised regional tensions – between Egypt, Ethiopia and Sudan – which have gained international attention and could hinder the livelihoods in downstream countries. A System Dynamics model was built for the entire Nile basin to explore the WFE nexus in the basin. The integrated simulation model considers a complete WFE nexus for Egypt while partial consideration for the rest of the countries. The integrated simulation model consists of two main components: (a) partial WFE nexus outside Egypt and (b) complete WFE nexus in Egypt. The two model components are linked through High Aswan Dam (HAD). The first component consists of a water resource model for the entire Nile basin with 72 basin-wide river inflow tributaries. The Nile water resource model incorporates key components that affect the system’s water management such as natural lakes, wetlands, water infrastructure (e.g., dams) and different water users. A simple crop yield model is linked to the Nile water resource model to account for food production from irrigated agriculture in the basin. Hydropower generation can be obtained from hydropower plants in the basin during model simulations. The second component, i.e., complete WFE nexus in Egypt, includes population, gross domestic product, water balance and food balance, while the energy sector includes hydropower generation from HAD and energy demand in food and water sectors. To account for the uncertainty and hydrologic variability in river flow regime, a stochastic simulation is applied. Model simulations are driven by basin-wide stochastically generated data that is either based on historical stream flows (for the case of no climate change) or climate change projection of stream flows (for the case of climate change). The integrated simulation model runs at a monthly time-step. Model calibration and validation showed a satisfactory performance and the model is fit for the purpose for which it is developed. The integrated simulation model was used to investigate the WFE nexus in the basin during the filling and subsequent operation of GERD using basin-wide stochastically generated river flows with no climate change. Results show that GERD filling during above-average years is likely to have a little impact on the downstream countries and it could accelerate the reservoir filling. Conversely, the reservoir filling during dry years is likely to cause significant impacts on the downstream countries. Once GERD comes online, it will generate an average of 15,000 GWh/year. Furthermore, model simulation results suggest further investigation and implementation of dynamic filling strategies that would maximize basin-wide benefits and reduce risks to downstream countries. At the national level, the developed model was used to investigate the impacts of implementing policy measures (e.g., improving irrigation efficiency, developing new water resources, improving land productivity) on the WFE nexus in Egypt. For instance, improving irrigation efficiency and land productivity offer promising outcomes to improve the future of the WFE nexus in Egypt. For instance, achieving the potential crop yields alone would increase food production by 40% and reduce food imports by 32%. The simulation model is also used to explore the cooperation over the GERD and its impacts on the WFE nexus on the downstream countries during the operation phase. Simulation results show that during dry years, the risks to Egypt (e.g., water shortages and food production loss) can be substantially reduced if the riparian countries agree to cooperate and sacrifice for some loss (i.e., loss in hydropower generation) especially during severe droughts. However, a high level of coordination, commitment and trust among the riparian countries are urgently required to achieve cooperation benefits. Basin-wide impacts of planned projects in the riparian countries are also analysed through different developments scenarios (e.g., hydropower development scenario, hydropower and irrigation expansions scenario) with and without climate change. Climate change is investigated here through two Representative Concentration Pathways (RCPs): RCP 8.5 and RCP 4.5 with two General Circulation Models (GCMs) per each climate scenario until 2050. Projected streamflow of river tributaries under climate change are used to generate basin-wide synthetic streamflow series to drive model simulations. Simulation results demonstrate that the WFE nexus in the basin is less affected by planned developments than climate change. The analysis of climate change scenarios indicated that climate change exhibits large uncertainty and is likely to have significant impacts on the river flow regime, food production and hydropower generation in the basin. The average annual river runoff is likely to reduce by 7% in the RCP 4.5, while RCP 8.5 showed a wider range of change from -40% to +33%. Following river flow changes, hydropower generation and food production in the basin are impacted in a similar way under climate change but with varying degree of change in sub-basins. At the general level, the novel framework developed in this work is a step forward for better understanding of the nexus interdependencies in river basins including but not limited to the challenging case of transboundary rivers. The novel framework addressed key nexus interlinkages and considered important issues such as uncertainty in river flow regimes, climate change and population growth. It can be beneficial in negotiations for transboundary systems, policy analysis, enhancing cooperation and trust among riparian countries, and promoting for cross-sectoral and cross-regional management. Systems-based approaches offer basis to improve our understanding of the interactions between the WFE nexus and other important issues in river basins. Furthermore, they allow for identifying trade-offs and synergies and improve coordination among sectors, countries and interested stakeholders.
... The water-energy nexus concept is based on the relationship between two resources, where policy decisions regarding energy can have positive and negative impacts on water resources and vice versa (e.g., Napoli and Garcia-Tellez 2016;Stillwell 2015). Pelli and Hitz (2000) were among the first to establish a water-energy relationship in WDNs. ...
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