Water Consumption in the World
The global water footprint is 7,450 billion m3/year which means 1,240 m3/year per person on average. The people in the United Stated have the largest water footprint at 2,480 m3/year per capita, followed by the people in south European countries such as Greece, Italy and Spain at 2,300 – 2,400 m3/year per capita. The size of the global water footprint is largely determined by the consumption of food and other agricultural products. The total volume of water used globally for crop production is 6,400 billion m3/year at the field level.
Types of Water Being Used
There are three different types of water that is used in the production of agricultural products, these are calculated into the water footprints above, which go into making the fashion products we know and love today. The three types of water are:
- Blue Water: Fresh surface and groundwater, in other words the water in freshwater lakes, rivers and aquifers.
- Green Water: The precipitation on land that does not run off or recharge the groundwater but is stored in the soil or temporarily stays on top of the soil or in vegetation.
- Grey Water: All of the wastewater generated in households or office buildings from streams without fecal contamination.
What does this mean for the footprint of each of these types of water? 83% of water used in agriculture is green water while the remaining 17% is blue water. Currently, recycled Grey Water, often referred to as Reclaimed Water, is being used only by select states as is can be costly to build the necessary wastewater treatment plants.
How the Number 1 Agricultural State is Changing How Water is Working for Them
Urban wastewater, after treatment to a suitable level, is a good substitute for groundwater or imported surface water for irrigation and other on-farm
uses. The California Water Recycling Criteria (encoded in Title 22 of the California Code of Administration) allow 43 specified uses of recycled
water—including irrigation of all types of food crops. These criteria include different water quality requirements for irrigation of each type of crop;
those eaten raw, those receiving processing before consumption, and those not involving any human contact before industrial processing. These regulations
are among the most stringent in the world and have been used as a model for many other countries’ guidelines and water reuse regulations. In California,
growers using recycled water meeting the Title 22 criteria have shown over the last 50 years that this practice is safe and economical. Recycled water is
also sustainable, conserves energy and provides a significant portion of the nutrients needed by the crops—nitrogen, phosphorus and micronutrients.
What water savings have been achieved you ask? Water savings achieved by using recycled water can range up to 100 percent of the demand, depending on the extent to which available recycled water must be supplemented with traditional sources of irrigation water. In some cases, river water or well water is supplemented with recycled water to produce a blend with a lower salinity than that of straight recycled water. Currently, farmers in California use roughly 250,000 acre-feet of recycled water each year for a wide variety of crops. There is significant opportunity to substantially expand the use of recycled water for agricultural irrigation. Using this recycled water also has significant environmental benefits by redirecting wastewater to fields that may otherwise degrade sensitive water bodies. Furthermore, recycling agricultural water can offset withdrawals from surface water, bolstering water flows for fish, other wildlife and plants.
Case Study – Cotton
The impacts of the cotton industry to the environment are easily visible and have different sides to them. The production of cotton can deplete water supplies and also impact water quality. The Aral Sea is the most famous example of the effects of water abstractions for irrigation. From 1960-2000, the Aral Sea lost approximately 60% of its area and 80% of its volume as a result of annual abstractions to irrigated the cotton grown in the desert. 50% of the cotton field in the world is irrigated which produces 73% of the cotton in the world. Irrigated cotton is mainly located in dryer regions: Egypt, Uzbekistan, and Pakistan. The province Xinjiang of China is entirely irrigated while Pakistan and North India a major portion of the water used must be supplementary irrigation. A result of these irrigated fields is the fallen water tables in Pakistan and China, making it harder for villages and families to dig wells and access freshwater. 70% of the world’s cotton crop production comes from China, USA Pakistan and Uzbekistan.
Although the chain from cotton growth to final product can take several distinct steps, there are two major stages: the agricultural stage (cotton production at field level) and the industrial stage (processing of seed cotton into final cotton products). In the first stage, there are three types of impact: evaporation of infiltrated rainwater for cotton growth, withdrawal of ground- or surface water for irrigation, and water pollution due to the leaching of fertilizers and pesticides. As shown above, both green and blue water use can be quantified in terms of volumes used per year. The impact on water quality is quantified here and made comparable to the impacts of water use by translating the volumes of emitted chemicals into the dilution volume necessary to assimilate the pollution. In the industrial stage, there are two major impacts on water: abstraction of process water from surface or groundwater (blue water use), and pollution of water as a result of the waste flows from the cotton processing industries.
To Learn More
Chapagain, A.K., A.Y. Hoekstra, H.H.G. Savenije, and R. Guatam. 2005. "The Water Footprint of Cotton Consumption." UNESCO-IHE: Institute for Water Education.
Gleick, Peter H. 2014. The World's Water. Washington, DC: Island Press.
Hoekstra, Arjen Y, and Ashok K Chapagain. 2008. Globalization of Water: Sharing the Planet's Freshwater Resources. Oxford: Blackwell Publishing.
Sheikh, Dr. Bahman. 2011. Use Of Municiple Recycled Water. Accessed August 10, 2016. http://agwaterstewards.org/index.php/practices/use_of_municipal_recycled_water#FAQ.