A water footprint is the total volume of water that is used to produce the goods and services consumed by an individual or group. The water footprint of an individual refers to the total volume of water used to produce the things that the individual consumes. The water footprint of a country or region is composed of the sum of the water footprints of its inhabitants.
The World Water Footprint Assessment Report estimates that the average global water footprint per capita is about 1000 m^³ (2641 gallons) per year. This is the equivalent of each person using 2000 liters (528 gallons) of water per day. The United States has the largest water footprint per capita, at about 1600 m^³ (4212 gallons) per year. This is more than double the global average and about 400% more than someone living in Uruguay, which has the lowest water footprint per capita, at about 200 m^³ (528 gallons) per year.
A person’s water footprint can be divided into three components:
Blue Water Footprint
A blue water footprint is the volume of surface and groundwater resources used to produce the goods and services consumed by the individual or group. It includes the consumption of rainwater stored in lakes, reservoirs and rivers (surface water) as well as groundwater from aquifers.
Green Water Footprint
The green water footprint is the volume of rainwater used directly by the crops and plants from which the individual or group consumes goods.
Grey Water Footprint
A grey water footprint is the amount of freshwater needed to assimilate pollutants that originate from the production process, such as wastewater discharged into rivers, lakes, or seas. It represents both the surface runoff from rainwater and irrigation return flow from crops.
It can also be expressed in terms of the amount of water used per unit of time, such as liters per day or gallons per year. For example, the average American’s water footprint is about 2,000 gallons (7,600 liters) per day. It can be used to assess the sustainability of different production practices and consumption patterns. For example, growing crops in drought-prone areas requires more irrigation water than growing them in areas with high rainfall. Therefore, the same crop grown in different places can have very different footprints.
Likewise, producing beef requires more water than producing chicken or vegetables because cattle need more water for drinking and for cooling as they eat their feed. Therefore, the water footprint of beef is typically larger than that of poultry or vegetables.
In addition to these production-based water footprints, we also have a consumption-based water footprint, which measures the amount of freshwater withdrawn or consumed by an individual or group through their daily activities, including cooking and bathing.
Although a water footprint is useful for measuring the local impacts of our consumption on freshwater resources around the world, it does not account for all of the ecological consequences associated with consuming certain products and services. For example, fishing can deplete fish stocks over time in oceans and lakes around the world because it is often more profitable to catch larger fish with longer life spans rather than younger fish with shorter life spans. In addition, cleaning the products that we consume (e.g., washing our clothes or dishes) can contribute to water pollution and subsequent ecological problems in the environment (e.g., increased algae blooms from discharging wastewater with higher nutrient loads).
Impact on Ecosystems
Ultimately, it can be used as an important tool for identifying and minimizing our impacts on freshwater ecosystems around the world, but it is equally important to consider other factors that affect water use and availability when making decisions about our consumption patterns. So while it’s certainly important to reduce our overall footprint by conserving water at home and choosing products that have a low footprint, we should also consider other environmental impacts associated with consuming these goods and services. For example, if we’re trying to reduce our footprint by eating less beef, we should also consider the significant impact that cattle ranching has on greenhouse gas emissions.
What is your water footprint?
Assuming you are doing all the necessary things to live a sustainable life, your footprint would be 740 gallons per day. However, if you take into consideration all of the things you do that might have an impact on water resources around the world, your number might be much higher. For example, if you eat beef or poultry, drink coffee or tea, or use products that are made with cotton, your footprint would be much larger.
It can be a useful tool for individuals and communities to assess their water use and identify ways to reduce their impact on freshwater resources. There are a number of online calculators that allow users to estimate their own footprints. These calculators typically ask questions about daily activities such as showering, laundry, and dishes to estimate water use. They also ask about the types of food consumed and how it was produced. For example, meat production requires more water than plant-based diets.
The footprint of staples may be surprising. For example, it takes about 2250 liters (595 gallons) of water to produce one kilogram (about two pounds) of rice. Coffee requires about 140 liters (37 gallons) of water per cup. A single hamburger requires about 660 liters (175 gallons) of water to produce. Avocados not only have a high carbon footprint, but they also require a lot of water to grow; it takes about 2000 liters (528 gallons) of water to produce one kilogram (2.2lbs) of avocados.
It can also be used to assess the impact of different production practices on freshwater resources. For example, conventional agriculture typically has a larger water footprint than organic agriculture due to the use of irrigation and other inputs.
Water footprints can be offset through a number of different practices such as water conservation, planting trees, and supporting projects that protect or restore freshwater ecosystems.