The shape of water

1st February 2019

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  • Energy ,
  • Water ,
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  • sea ice loss ,
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Carbon footprints can help us mitigate climate change, and water footprints can do the same for water management, explains Rick Gould.

Strong evidence suggests that over-consumption is the principal cause of water scarcity. Global freshwater use has increased nearly sevenfold during the past century, while water withdrawal has consistently outpaced population growth since 1940. Unsustainable water use creates crises – so much so that, in 2014, the World Economic Forum declared the potential impacts of water crises to be the largest worldwide environmental and social risk.

A deepening crisis

“We see water crises worsening all over the world and increasing water scarcity,“ says Rick Hogeboom, executive director of the Water Footprint Network (WFN). “Four billion people live in a region of water scarcity for at least one month of the year.“

No aspect of life – ecological, agricultural, political, social and economic – is unaffected by water shortage. “All economic activity depends on clean water, and water scarcity means an economic downturn,“ explains Hogeboom. In 2016, for example, the World Bank predicted a 6% fall in global GDP by 2050 if water scarcity continues to grow.

Is climate change the issue here? “The real problem is our growing population and affluence,“ says Hogeboom. Affluence means more consumption, higher energy use and a diet richer in meat – all activities that involve high water consumption. Measuring and monitoring water use is a starting point for tackling the problem, and this is where 'water footprints' (WFs) can play a key role. What are they, and how can we use them?

Tracking the footprints

A WF is the total volume of water needed to produce and use a product or service during its life-cycle. This includes the water sources, whether these are direct or indirect. The concept was developed by Professor Arjen Hoekstra in 2002, when he was working at the UNESCO-IHE Institute for Water Education. He wanted to create a metric to measure the amount of water consumed and polluted to produce goods and services along their supply chain.

Hoekstra himself explains further. “That same year, we were the first researchers to estimate WFs of different countries by tracing indirect water use in international trade.“ Traditionally, water use was gauged by simply looking at freshwater abstraction and where the water was used. Hoekstra saw that this was simplistic and wanted to develop a methodology that included transboundary flows. This method also calculates 'virtual water trade', which is the water virtually embedded in traded commodities. In this sense, virtual water is analogous to embedded carbon.

A WF considers three components – green, blue and grey water footprints, and considers both direct and indirect water-use. “A multi-dimensional WF tells you when and where water is consumed and polluted,“ says Hogeboom. “It gives more information than just a national withdrawal of freshwater.“

Hoekstra and his team have examined the WFs of hundreds of crop and animal products, and traced all virtual water flows between nations, calculating WFs from product level up to national level. The data revealed that many countries are either net importers or net exporters of water – and it is environmentally risky for a country to be a long-term net water exporter, especially if there is a net overall loss in supplies.

Research into action

Researchers worldwide have embraced WFs since 2002, and their results are enabling a growing number of organisations to manage water more sustainably. Hoekstra and his team, for example, have characterised WFs for numerous products: Figure 1 shows the WFs for several widely used animal and plant-based products. Hoekstra's team has also researched the WFs of different European diets, finding that southern European consumers typically have a larger WF than those in northern Europe, due to higher meat consumption. Europe collectively appears to be a large importer of water: about 40% European consumers' WF lies outside Europe. Consuming less meat will reduce Europe's WF considerably.

As the research evidence grew, Hoekstra's team further developed the WF methodology and processes of flow mapping, water-use accounting, efficiency and sustainability assessments. The result was a comparable and scientifically robust metric, while the methodology evolved into the Water Footprint Standard in 2009. The concept was strengthened when companies such as Coca-Cola and Unilever saw the value in using WF assessment to identify risks and reduce their impacts.

The Water Footprint Network sprang from this work, evolving in order “to maintain the Standard and serve as a focal point for research, data and exchanging information,“ according to Hogeboom.

Two steps forward

The International Standards Organisation (ISO) has also developed a standard, ISO 14046, for calculating WFs. How does it compare to the Water Footprint Standard? “Our standard is a volumetric measure of pressure on water, whereas ISO 14046 is a measure of impact,“ says Hoekstra. “There is some overlap, but they have different aims.“

The Water Footprint Standard is a generic approach that can be applied to assess the WF of products, companies, individual consumers and even countries, whereas the ISO standard focuses on “estimating environmental impacts of water consumption, and does not include rainwater or polluted water,“ Hoekstra explains. As such, it is aimed at assessing environmental impacts of water use of products in the context on a Life Cycle Assessment (LCA) and the ISO 1404x series of LCA standards. In this way, the WFS and ISO 14046 serve different and even complementary roles.

Hoekstra is hopeful that the role of WFs will develop further and become more prominent. “I expect that, in due time, companies are going to set WF reduction targets – not only for their own operations, but for their supply chains as well,“ he says. He has also proposed that governments would find it beneficial to set WF caps for river basins. “Without any agreed limit to water consumption and pollution, how can we expect to stop water depletion and pollution beyond the carrying capacity of a water basin?“

A thirsty planet

  • Biofuels production has increased significantly during the past decade, with a big impact on water demand. One litre of biofuel needs between 1,000 and 4,000 litres of water to make it.
  • From 1996 to 2005, the global annual average WF was 9,087 gigametres3. About one-fifth of the global WF relates to production for export.
  • The global annual average per capita WF is just under 1,400m3. The average US consumer has a WF of about 2,850m3.
  • About 91% of a consumer WF is due to the consumption of agricultural products, 5% is from industrial goods and 4% is from domestic water use.
  • Water abstraction strongly correlates with industrialisation, energy consumption and population growth. The biggest growth in demand is in Asia. Demand is stable in Europe, but the UK is still one of eight nations that the European Environment Agency regards as water-stressed.
  • A meat-rich diet consumers disproportionately high amounts of water and energy, with beef being the 'thirstiest' meat product.
  • Europe is a net importer of virtual water due to its meat-rich diet and international food trade.

Rick Gould, MIEMA CEnv, is a technical advisor at the Environment Agency. He is writing in a personal capacity

Image credit: iStock


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