It's pretty easy to control how much water you use and conserve -- you turn off the tap when you brush your teeth, you only do laundry when you have a full load and sometimes you even "let it mellow" in the toilet. These are all examples of direct water use (i.e. water you use by turning on and off a tap).
Most of your daily water use, however, comes indirectly from the food you eat (water for irrigation, especially for feed stock for the animals we eat), the energy you use (water for power plant cooling and extracting and refining fossil fuels) and the products you buy and use (water for extracting, refining and manufacturing). It's more difficult to measure and reduce this virtual water use. You can't see it and you can't help but use it, so what exactly is virtual water? It's all the water it took to grow, process, manufacture and transport the food, goods and services that you eat, consume and use every day.
Here's an example.
Your cellphone may not be waterproof but it took water to make it! The phone is made of plastic, metal and glass components, and each requires virtual water* to produce. Here's why:
- Plastics are derived from oil that was drilled out of the ground, sent to a refinery and turned into plastics pellets which are then sent to a manufacturer and formed into plastic parts. Each of these processes requires water to complete. The plastic parts are then sent to the cellphone manufacturing plant using transportation fuels that require water for extraction and refining.
- Metals are extracted from mines, sent to a refinery and formed into metal pieces. Both processes require water. The metals are then sent to the cellphone plant, using transportation fuels that require water for extraction and refining.
- Glass is made from silica that is extracted from a quarry, sent to a refinery and made into glass parts. Each of these processes requires water. The glass parts are then sent to the cellphone plant for assembly, using transportation fuels that require water for extraction and refining.
- Once the phone is assembled, it's packaged and sent to stores. So there's more water required to produce packaging, and of course, for the transportation fuels.
This doesn't even include the water required to produce the energy it took to complete all those steps! As you can see, virtual water runs deep.
The volume of water required for each of these processes and steps adds up quickly but measuring exactly how much we use is difficult. Every five years, the USGS estimates daily US water withdrawals for uses like agriculture, energy production and commercial/industrial processes. According to the 2005 data (the most recent data set available):
- 49 percent of daily US withdrawals go to thermoelectric power generation;
- 31 percent of daily US withdrawals go to agriculture; and
- 4 percent of daily US withdrawals go to industrial processes; whereas,
- 11 percent of daily withdrawals are for public supply.
Clean energy sources like solar and wind use very little water to produce power. Find out how clean your energy mix is with this EPA Power Profiler.
It's easy to see, given these percentages, that most of your water footprint comes from virtual water use. In fact, your water footprint is heavily influenced by the type of diet you eat. A diet that's more reliant on meat and dairy products has a higher water footprint because it takes a lot of water to grow the grain that the livestock eats. In addition, processed foods require more water than whole foods because there are more water-intensive steps involved in order to get food to you, including transporting food from the farm to the processing facility, then to the store, processing food at a plant, and finally wrapping it in all that packaging. Think about that the next time you're about to eat a big ole' fast food cheeseburger or are buying lots of packaged food at the grocery store.
Your water footprint is also heavily influenced by the predominant form of energy production in your state. Areas that rely heavily on thermoelectric power - especially coal-fired power plants - have higher water footprints because a lot of water is required for cooling. Additionally, although hydroelectric power is considered a renewable energy source, it has a high water footprint because significant amounts of water can evaporate from the surface of reservoirs created by dams.
If you want to reduce your water footprint, food and energy offer opportunities that you might not have realized. Changing how you eat and how and where you get your electricity are great ways to start. Here are some suggestions:
- Eat lower on the food chain - it takes less water to grow and produce vegetables, fruits, nuts and legumes than it does to produce meat and dairy products from grain-fed animals. Farmers raising sustainably grown animals that are completely pasture raised often take water use into account and have much lower water footprints than grain-fed animals. Seek out these sources for meat and dairy.
- Eat more whole foods, which use less virtual water than processed food.
- If possible, install renewable energy sources like solar and wind power on your property - or sign up for renewable power through your utility - because they use very little water to produce electricity.
- Look for opportunities to become more energy efficient, by doing something simple like changing your light bulbs or more complex like buying energy efficient household appliances. Remember, by saving energy, you also save water.
You can find out more about your water footprint and learn ways to conserve and use water more efficiently by taking GRACE's Water Footprint Calculator.
*The exact amount of water required to make a cellphone is not available as of this publication date, but check out this Treehugger article to find out how much water it took to make a car, a pair of jeans or a to-go latte.
The water used in producing just about anything can be measured and evaluated along the life cycle of the product to determine its water footprint. The Water Footprint Network has evaluated the water footprint of many food items and some textiles products and has assembled an online gallery showing how many gallons it takes to produce these items.