Connessione tra acqua ed energia

A fundamental link

An approach that takes into account the close connection between water and energy would lead to significant steps forward on some of the main challenges of our times: tackling climate change, ensuring energy security and providing energy, drinking water and sanitation to the billions of people who lack these today.

by Molly A. Walton
11 min read
by Molly A. Walton
11 min read

This article is taken from World Energy (WE) number 46 – Water stories

Energy and water have always been closely intertwined; water is needed for all phases of energy production and energy is critical to water supply, wastewater treatment and desalination. How this nexus is managed is critical for the energy community as it has implications for the transition to a low carbon pathway, energy security and the attainment of the Sustainable Development Goals (SDGs).  

Analysis by the International Energy Agency (IEA) found that the energy sector withdraws around 340 billion cubic meters (bcm) of water—defined as the volume of water removed from a source—and consumes roughly 50 bcm—the volume that is withdrawn but not returned to the source.  This amounts to 10 percent of total global water withdrawals and 3 percent of consumption. While the energy sector’s share is relatively low, global water demand could increase by 30 percent by 2050 (UN Water, 2019). 

On the other side of the energy-water equation, the IEA found that the water sector uses almost as much energy as Australia. Most of this is in the form of electricity—850 terawatt-hours (TWh) primarily for water supply and wastewater treatment—and represents around 4 percent of global electricity consumption. In addition, some 50 million tons of oil equivalent of thermal energy is used for desalination and diesel pumps for irrigation.

With both energy and water demand on the rise, it is increasingly important to understand the water-energy nexus in order to avoid unintended consequences, anticipate stress points and implement policies, technologies and practices that soundly address associated risks and maximize synergies.

How much water does a low-carbon pathway need?

While the energy transition can provide significant environmental benefits, the fuels or technologies used to achieve this transition can, if not properly managed, exacerbate or introduce water stress depending on the location, availability of water and competing users. Similarly, a lack of water could limit the options available to pursue a low-carbon pathway. While some low-carbon technologies such as wind and solar PV require very little water, others, such as biofuels, concentrated solar power (CSP), carbon capture, utilization and storage or nuclear power are relatively water-intensive. This underscores the importance of factoring water use into all energy policy decisions.

IEA analysis, which assessed the future water needs of various potential energy scenarios, found that an integrated approach focused on tackling climate change, delivering energy for all and reducing the impacts of air pollution (our Sustainable Development Scenario) results in lower water withdrawals in 2030 relative to today (see Figure 1). This is due to the increased deployment of solar PV and wind, a shift away from coal-fired power generation and a greater focus on energy efficiency.  As a result, withdrawals in the Sustainable Development Scenario are much lower in 2030 than they are in a scenario based on current trends and policies (our Stated Policies Scenario).

Comparatively, the energy sector’s water consumption rises in both scenarios relative to today (Figure 2). The rise in consumption in the Sustainable Development Scenario is underpinned by a shift to more wet-tower cooling in the power sector, a rise in nuclear and greater reliance on biofuels in transport. Moreover, consumption accounts for a higher share of the energy sector’s water withdrawals in this scenario (26 percent). Though water withdrawals are the first limit for energy production when water availability is constrained, water consumption reduces the overall amount of water available to satisfy all users.

Many of the climate impacts will be felt through water, which has implications for energy security

Water scarcity is already having an impact on energy production and reliability, and further constraints may call into question the physical, economic and environmental viability of future projects. On the other side, diminished freshwater resources can lead to a greater reliance on energy-intensive sources of water supply such as desalination. Each of these have potential implications for energy security. 

Many countries already face some degree of water stress, and there is increased uncertainty about future water availability and the impact that climate change will have on water resources. Climate change is expected to alter the frequency, intensity, seasonality and amount of rainfall as well as the temperature of the resource, with an impact on both energy and water infrastructure. 

Several countries that are large energy consumers, such as India, China and the United States, may find that their plans to increase power generation in some parts of the country will be dependent on water availability.  Droughts and water shortages have already affected India’s thermal power plants: India lost 14 terawatt-hours (TWh) of thermal power generation in 2016 due to water shortages (Luo et al., 2018). Rising temperatures may also mean some power plants are no longer able to comply with the temperature regulations for water discharge. Thus, plans for power generation that rely on more water-intensive technologies will need to take into account current and future water availability in the choice of sites and cooling technologies, and, where possible, use alternative water sources. 

Hydropower, which plays an important role in many countries’ decarbonisation plans, is especially vulnerable to climate impacts.   Hydropower accounts for 22 percent of electricity generation in Africa, compared to 16 percent globally. Climate change has already affected the capacity of Zambia’s largest hydropower plant, leading to power blackouts.

Rising water demand coupled with increasing uncertainty over water supply could lead more countries to turn to desalination to help narrow the gap between freshwater withdrawals and sustainable supply. This would come with an energy cost. Take the Middle East as an example: desalination accounts for just 3 percent of the Middle East’s water supply today but 5 percent of its total energy consumption. By 2040 in the Stated Policies Scenario, it is expected that desalination will account for roughly a quarter of the region’s water supply and almost 15 percent of total final energy consumption. Using water more efficiently and tackling water losses from pipe leaks, bursts and theft can help mitigate the increase in energy demand and increase water availability. If all countries were able to reduce water losses to a level seen in the best-performing countries, the equivalent of the entire annual electricity needs of Poland could be saved today.

Energy has a role to play in attaining SDG 6

More than 2.1 billion people lack access to safe drinking water. More than half the global population lacks access to proper sanitation services. More than a third is affected by water scarcity. And roughly 80 percent of wastewater is discharged untreated, thus adding to already problematic levels of water pollution. Energy is an essential part of the solution to these challenges, and IEA analysis shows that achieving universal access to clean water and sanitation would add less than 1 percent to global energy demand in its Sustainable Development Scenario by 2030.

Several synergies emerge when the SDGs are viewed through an integrated lens, especially between SDG 6 (water and sanitation for all) and SDG 7 (energy for all). In rural areas, almost two-thirds of those who lack access to electricity also lack access to clean drinking water (Figure 3). As a result, considering water supply needs when planning electricity provision can open different pathways for both and lower the cost of electricity for households.  The production of biogas from waste can facilitate cleaner cooking in households that currently rely on wood and charcoal for cooking. When wastewater management in urban areas requires new infrastructure, integrating energy efficiency from the start can have a significant impact on the energy and GHG emissions footprint of the wastewater sector. Moreover, harnessing the energy embedded in wastewater can allow wastewater utilities to become energy producers.

That said, providing access is just the start as it is critical to ensure that  it is reliable, affordable and scalable in order to meet the rising demand that results from population growth and increasing standards of living. Where water services can provide an “anchor load” for power generation, approaching water and electricity in an integrated way may shift the emphasis towards more mini-grid or grid-connected solutions instead of off-grid solutions. Moreover, beyond just the household level, the provision of energy and water for productive uses, such as agriculture, can foster economic opportunities and create a stronger business case for entities to invest in related infrastructure.

SDG 6 is also about ensuring that water is used more efficiently. While the energy sector’s share of total global water use is relatively low, it could be reduced further. Changes in the fuel and technology mix, improving power plant efficiency, deploying advanced cooling systems, and making better use of non-freshwater and water recycling can not only help the energy sector improve its water use efficiency and contribute to SDG 6 but also improve its resilience against climate change.


Water does not have to be a limiting factor for the energy sector and a rise in water demand does not have to be accompanied by a similar increase in energy demand. However, tackling climate change, shoring up energy security and ensuring progress on the SDGs will require that energy and water be considered in tandem.  

The good news is that many of the policies and technologies needed to reduce water and energy demand and ease potential choke points already exist. These include integrating energy and water policymaking, taking current and future water availability into consideration in the choice of power plant sites and cooling technologies, co-locating energy and water infrastructure, utilising the energy embedded in wastewater, using alternative sources of water for energy and improving the efficiency of both sectors.

A coordinated approach to development between the water and energy communities could also unlock significant progress on some of the most deep-rooted issues of our day: providing electricity, clean cooking, clean drinking water and sanitation to the billions of people who lack these today. This will require innovative business models, cross-sectoral planning and a well-designed regulatory framework that allows for the integration of decentralized solutions into the grid should it arrive. Additionally, co-ordination and financing will be vital to ensure that the necessary infrastructure, technical and financial knowledge, capacity and access to markets are in place.

The author: Molly A. Walton

She is an energy analyst with the World Energy Outlook (WEO) at the International Energy Agency (IEA). In this capacity, she leads the IEA’s analysis and engagement on the water-energy nexus and co-led the WEO-2017 special report on energy access.