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Erica Gies

Water and Food Security: Inextricably Linked

There's no food production without water. But water is becoming increasingly scarce. What are we using it for?

In a world where 1 billion people are already undernourished, according to the Food and Agriculture Organization, food insecurity is growing due to factors including population growth, climate change, and water insecurity. Of course, access to water affects agriculture. How it is allocated is something within our control and must be reevaluated if we are to feed a markedly larger population in the coming years.

And the world's population is growing, set to pass 9 billion by 2050. Those extra mouths are expected to increase global food demand as much as 70 per cent, according to the FAO. Population will grow mostly in areas where women still lack access to birth control and education, bulging to 2.2 billion in south Asia and an eye-popping 5 billion in sub-Saharan Africa, a more than 5-fold increase from the 900 million today.

Changing diets due to socioeconomic improvements, particularly in the BRIC countries – Brazil, Russia, India, and China – will also increase food demand, particularly for resource-intensive meat.

However, just when we need more, food supplies may be on the wane. A 2009 UN Environment Programme report found that world food production could decrease by 25 per cent during the 21st century. Water scarcity is a key factor.

Water stress

Like food insecurity, water insecurity is also on the rise, due to population growth, climate change, failing infrastructure, misallocation, and inefficient use.

"Water use grew at more than twice the rate of population increase in the 20th century."

During the 20th century, water managers planned for the future based upon the amount of water natural systems had provided in the past. But climate change is increasing variability in precipitation: greater fluctuations in watershed flows, less snowfall, earlier snow melt, rising temperatures in water bodies, altered stream channels and floodplains, saltwater intrusion, widespread drought in some places, floods in others. Longer, hotter summers are increasing pressure on water and electricity supplies.

Water use grew at more than twice the rate of population increase in the 20th century, according to a 2011 UN report on water. It found:

  • Around 700 million people in 43 countries, primarily in North Africa, South Asia, and parts of sub-Saharan Africa, experience water scarcity.
  • By 2025, 1.8 billion people will be living in areas of absolute water scarcity, and two-thirds of the world's population could be living under water-stressed conditions.

These factors mean that competition for water is intensifying among different sectors: municipalities, industry, agriculture and the environment. However, if each sector can reduce waste and if new laws can make allocation more flexible, there can be enough water to ensure food security.

Although only 20 per cent of the world's crops are irrigated, they suck up 70 per cent of all freshwater humans withdraw from rivers and aquifers. Almost half of the world's irrigated area lies in China, India, Indonesia, and Pakistan, providing more than half those countries' domestic food production. In some cases, this isn't sustainable. India, for example, already has a well-documented problem of groundwater overextraction. Unfortunately, some currently nonirrigated areas are among those likely to see an increase in drought with climate change, so they too may need supplemental water in the future.

"It takes far more water to produce meat calories than an equal amount of plant-based food."

Residents of BRIC countries are eating more meat, which is also problematic from a water sustainability perspective. It takes far more water to produce meat calories than an equal amount of plant-based food. For example, 1 kilo of rice requires about 3,500 litres of water, while 1 kilo of beef needs 15,000 litres, according to the UN. These dietary shifts have had the greatest impact on human water consumption over the past 30 years.

There are many ways to use water more efficiently in agriculture, including drip irrigation, planting crops that will thrive with available rainfall, irrigating with wastewater or other nonpotable water. But reducing water use in other sectors will also leave more wiggle room to support food security, both directly, for irrigation, and to sustain ecosystems, which support agriculture in complex ways.

Healthy ecosystems provide many things we value, such as natural flood control, water cleaning and storage, rich soil to grow our food, habitat for key pollinators, fish, and wildfowl. The way that agricultural water is managed currently has caused harmed ecosystems, weakening these ecosystem services.

Lightening energy's water footprint

Next to agriculture, energy generation uses more water than any other human endeavour, and in some developed countries, more water goes to energy generation. For example, in the United States, thermoelectric power generation — primarily coal, nuclear, and natural gas — accounted for 41 per cent of US freshwater withdrawals in 2005, while irrigated agriculture took 37 per cent, according to the United States Geological Survey.

"It takes a lot of water to produce energy, and it takes a lot of energy to move and treat water."

It also takes a lot of water to produce energy, and it takes a lot of energy to move and treat water. This interdependency is called the water-energy nexus. In the last decade, lack of water availability has sometimes halted energy generation at nuclear plants in Australia, France, Germany, Romania and Spain. Now water managers, governments, and international agencies are beginning to pay more attention to the water-energy nexus. For the first time in 2012, the International Energy Agency (IEA) reviewed water requirements for different energy sources in various regions. It predicted that access to water could become increasingly challenging for energy producers around the world.

Energy's water use is measured in two ways: withdrawals (short-term use) and consumption (long-term use). Worldwide, energy generation uses 15 per cent of water withdrawals, and that is likely to increase by one-fifth between 2010 and 2035, according to the IEA.

Water consumption for energy generation is set to rise by 85 per cent during the same period, more than double the rate of energy demand growth. "These trends are underpinned by a shift towards higher efficiency power plants with more advanced cooling systems (that reduce overall water use but increase consumption) and expanding biofuels production," according to the report.

Once-through cooling

Older thermoelectric plants (nuclear, coal, gas) use a process called once-through cooling. A typical 500-megawatt power plant takes in almost 19 million gallons of water an hour. The water is run through the plant and then most of it is deposited back into the water body a few minutes later, warmer and potentially polluted.

As old plants are retired, once-through cooling is being replaced by wet cooling, an evaporative method that withdraws just 3 per cent of the water needed for once-through but loses 90 per cent of that to vapour – so it withdraws less water but consumes more of it. It also has an energy penalty, using 3 per cent more energy for cooling than a once-through plant. A newer process called dry cooling uses fans to push waste heat into the atmosphere but has an up to 15 per cent energy penalty.


Biofuels consume water during irrigation and production. Compelling questions remain about whether it's worth doing from an environmental perspective. Crops such as corn ethanol drive up food prices, consume a lot of water, and may not be a net positive from a carbon emissions point of view.

"Crops such as corn ethanol drive up food prices, consume a lot of water, and may not be a net positive from a carbon emissions point of view."

The two largest biofuels producers are the United States (corn ethanol), and Brazil (sugarcane ethanol), which accounted for 87 per cent of global production in 2011. Countries considering expanding their biofuels production would do well to consider these examples, as true impacts are revealed at scale. Consider the US experience:

In 2010, 33 per cent of the US corn crop went to ethanol production, thanks to subsidies. However, concerns about land use, pollution, and especially water use in light of last year's major drought that increased grain prices prompted the US Congress to allow the subsidies to expire at the end of 2011.

Water and land use costs for corn ethanol are significant: According to a 2009 US Government Accountability Office report, 12 states produced 95 per cent of US ethanol in 2007, using 7 to 321 gallons of water for corn irrigation for every gallon of ethanol produced. Aside from irrigation, processing ethanol also uses water. Modern plants use about three gallons of water to produce one gallon of ethanol.

Corn ethanol's land use requirement is also problematic. A 2009 study by Jan F. Kreiger, a University of Colorado chemical engineer, found that at just 25 per cent gasoline displacement, corn ethanol would require 180 gallons of water per gallon of fuel and use 51 per cent of all US cropland.

Last fall, in response to criticism that biofuels targets were increasing world food prices, the European Commission reduced its target to 5 per cent, according to Reuters.

Biofuels that use waste materials as a feedstock and require no additional water are worth exploring. But subsidies for biofuels that use cropland and irrigation water will increase water for energy production and decrease food and water security.


The United States has also been on the cutting edge of hydraulic fracturing to harvest natural gas, and now other countries are considering it. Again, the US case is informative.

To frack a well, millions of gallons of water, chemicals and tiny particles of sand, quartz or ceramics are pumped into buried shale rock formations. The high-pressure liquids crack apart the rock, and the sand holds open the fractures, allowing gas to the surface.

"In some regions, farmers are already competing with gas companies for water rights."

Fracking has come under fire for various reasons, including concerns that it uses too much water and that it might pollute drinking water. The average well requires an average of 500 million gallons of water, but whether that use is a hardship to other water users is region specific. Lack of water has delayed fracking in China and slowed drilling in Texas. In some regions, farmers are already competing with gas companies for water rights.

But fracking uses just a fraction of local water consumption in Pennsylvania, the heart of the famous Marcellus formation, said John Veil, a consultant specializing in water and waste management issues for energy industries. It was just 0.29 per cent of total water withdrawals in 2011.

The possibility of water contamination is likely a bigger threat to drinking and irrigation water. Gas companies add several chemicals to the water, including biocides to kill bacteria from deep underground, scale inhibitors to reduce minerals that clog pipes, and lubricants for the smooth operation of pumps and other machinery.

"This wastewater is a particular pollution threat, as none of the current disposal methods are foolproof."

Some of the injected fluids flow back to the surface. Additional water that naturally occurs in deep rock also comes out with the gas, and it contains salt and sometimes radioactive elements. This wastewater is a particular pollution threat, as none of the current disposal methods are foolproof.

The most widespread method in the United States is to dispose of industry waste deep underground via "injection wells," which are primarily old oil and gas drill holes. The US Environmental Protection Agency supports the practice as a way to protect soils and surface water from contamination.

However, injection wells can leak. A recent investigative report by the news agency Pro Publica found that wastewater surfaced in several states, and thousands of wastewater injection wells failed safety tests so they are at risk of leaking.

Some gas companies dispose of fracking wastewater in municipal sewage treatment plants. However, these plants were not designed to treat this waste stream and can pass radioactive compounds, cancer-causing chemicals, and inadequately treated sewage into local rivers.

Another disposal approach is for gas companies to treat wastewater onsite and reuse the water in future fracks. However, this can be energy intensive and costly. Gas companies also sometimes sell the byproduct – a super salty waste called brine that contains heavy metals and other pollutants – to state transportation departments to melt highway snow in winter and suppress dust in summer, and the runoff moves salts and chemicals to rivers.


Renewable energy sources, such as solar and wind, have a much lighter water footprint. They require some water in manufacturing but little in operation.

"Hydropower raises serious sustainability questions. The developing world is currently on a dam-building boom, but that may prove to be a waste of money."

Hydropower, on the other hand, raises serious sustainability questions. While dams have helped many regions grow more food than they otherwise could with rainfall alone, hydropower consumes many times more water than thermoelectric generation because of evaporation from the lake created behind the dam. The developing world is currently on a dam-building boom, but that may prove to be a waste of money as newly dammed rivers run low.

Dams also undermine food security by causing dramatic changes to ecosystems. The flooding behind the impoundment warms and slows rivers, changing the habitat. Dams decrease floodplain fertility by reducing or eliminating nourishing floods. They impede fish migration and reproduction. Ironically, they also lead to increased erosion and flooding by reducing the flexibility of a natural hydrological system.

To best juggle all these competing factors and interests, we need to apply systems-level thinking to the water-energy nexus using new software and hardware technologies. We also need to scale up renewables and reevaluate water rights laws and pricing structures to increase flexibility and resilience in water management and to incentivise efficient use.

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