You might be surprised by how big the water footprint of food is. In the US, agriculture is responsible for 80 percent of all water consumed (water that is evaporated or otherwise removed from the watershed).
The Big Water Footprint of Food and Agriculture
California experiences frequent multi-year extreme droughts – like the one occurring now – that are hard on the state’s agricultural industry. As California is the top agricultural producing state in the country, the droughts serve to raise awareness about just how much water it takes to produce food.
In the US as of 2015, irrigation accounted for 42 percent of the nation’s freshwater withdrawals. Agriculture accounted for the majority of those withdrawals, and it accounts for approximately 80 to 90 percent of the nation’s consumptive water use. In fact, agricultural withdrawals account for 69 percent of water use around the world.
The Water Footprint of Food is Big
Put simply, producing food requires a lot of water. The Water Footprint Network (WFN) has calculated how much water it takes – called a water footprint – for a large number of food items. Table 1 lists foods common to a US diet and the water footprint of a typical serving for each.
Table 1. Water Footprint of Eight Common Food Items
|Food Item||Serving Size||Water Footprint|
|Steak (beef)||6 ounces||674 gallons|
|Hamburger||1 (includes bread, meat, lettuce, tomato)||660 gallons|
|Ham (pork)||3 ounces||135 gallons|
|Eggs||1 egg||52 gallons|
|Soda||17 ounces||46 gallons|
|Coffee||1 cup||34 gallons|
|Wine||1 glass||34 gallons|
|Salad||1 (includes tomato, lettuce, cucumbers)||21 gallons|
As Table 1 indicates, meat (in this case, pork and beef) requires the highest amount of water to produce. In fact, as many people who have taken GRACE’s Water Footprint Calculator (WFC) have learned, diet overwhelmingly makes up the largest part of a person’s water footprint, even when compared to taking long showers or flushing the toilet every time it’s used (these types of water uses matter but have less of an impact). Why Is Food’s Water Footprint So Big?
The reason the water footprint of food is so big has to do with the three parts of a water footprint: the blue, green and grey water components. Each part represents the volume of water consumed, evaporated and polluted when an item is produced.
The WFN (whose research provides some of the data used in the WFC) defines these components as:
Blue Water Footprint: The amount of surface water and groundwater required (evaporated or used directly) to produce an item – for food this mainly refers to crop irrigation.
Green Water Footprint: The amount of rainwater required (evaporated or used directly) to make an item – for food this refers to dry farming where crops receive only rainwater.
Grey Water Footprint: The amount of freshwater required to dilute the wastewater generated in manufacturing, in order to maintain water quality , as determined by state and local standards – for food this refers to things like field and farm runoff.
Comparing the Water Footprint of Meat to Fruits and Vegetables
The numbers are especially high for meat and animal products like dairy and eggs because animal feed typically comes from either irrigated or rain-fed grains or rain-fed forage (like grass), both of which have large blue and green water footprints.
Animals that are factory farm- or feedlot-raised (which the majority of livestock in this country are) consume feed that is primarily composed of corn and soy, both of which rely on high amounts of irrigation and rainwater – the blue and green water footprints.
Irrigation comes from surface and groundwater sources that are often also claimed by other users like energy companies and urban areas or are required to keep aquatic habitats healthy.
By contrast, animals that are raised on pasture eat forage which primarily relies on rainwater – the green water footprint. However, grass-fed animals take longer to get to market weight, so meat from those animals will have a higher green water footprint than their factory-farmed counterparts , but the blue water footprint will be significantly lower.
In addition, there is less likely to be competition for water resources for animals that rely on rain-fed forage. Well-managed pasture operations also have lower grey water footprints (the water required to manage pollution) than factory farm or feedlot operations. It should be noted that the only way to precisely measure water use in a particular operation is to conduct farm-level water use audits or water footprint assessments.
Because meat and animal products have such a high water footprint, eating lower on the food chain can be a good strategy for reducing the water footprint of food required to meet daily dietary needs. It is also worth noting that while most produce has a lower water footprint than meat, certain items like nuts can have high irrigation requirements. This was especially problematic during the extreme drought in California due to the water required to keep nut trees healthy and producing.
Given all the water requirements of agriculture, there are more sustainable farming methods that strive to take water conservation into account, which can make farms more resilient to water issues like drought and competition for water resources.
Regenerative agriculture, permaculture and organic farming aim to use resources wisely to improve the quality and productivity of soil so that it retains moisture, minimizing the need for excessive irrigation. Recent technological advances in hydroponic, aquaponic, aeroponic and vertical farming make it possible to grow produce very efficiently, minimizing water use in a variety of locations. While no one farming method is perfect, they all can work together to create local and regional food systems that build agricultural resilience.
Food Waste and Water Footprints
Because it takes so much water (and other resources like fossil fuels, land and labor) to produce food, food waste has some pretty big implications. According to the NRDC, “forty percent of the food in the United States is never eaten. But at the same time, one in eight Americans struggles to put enough food on the table.” Wasted food means wasted resources, including water. This is why work is being done at every level – from local to federal – to reduce food waste. Activities like taking a refrigerator inventory before you shop, meal planning, using leftovers and composting can make a huge dent in the amount of food (and water) that is wasted on a daily basis. How Big Should My Food Water Footprint Be? Nobody will have a water footprint of zero from food because everybody has to eat. Still, choices about how and what to eat can help reduce daily water impacts from your diet.
Are you an educator?
Check out our free, downloadable lesson plans that help students understand the water footprint of food and their own dietary water use.