Water footprint

A blue water footprint refers to the volume of water that has been sourced from surface or groundwater resources (lakes, rivers, wetlands and aquifers) and has either evaporated (for example while irrigating crops), or been incorporated into a product or taken from one body of water and returned to another, or returned at a different time. Irrigated agriculture, industry and domestic water use can each have a blue water footprint.[6] According to “Evaluation of Environmental Impacts Due to Blue Water Consumption in China from Production and Consumption Perspectives.” by Multidisciplinary Digital Publish Institute it claims that “Based on the study of Kummu et al., the global blue water consumption per capita has increased from 209 m3/(year∙capita) in the 1900s to 230 m3/(year∙capita) in the 2000s, and total blue water consumption increased fourfold within the same period when taking the increase of the global population into consideration.”[7] Blue water consumption as shown in this article, is a huge part of everyday lives based off of the drastic increase between the years.  “We use blue water scarcity to measure the environmental sustainability of the blue water footprint. It’s a measure of the blue water footprint compared to the water available after considering environmental flow requirements. When the blue water footprint is larger than the available water, environmental flows are not met and over time, freshwater ecosystems degrade”, says Water Footprint Network in the “What is Water Footprint” article.[8] Based on this article, maintaining a consistent blue water footprint can be highly advantageous, but it can also become a problem if it grows too big and isn't taken care of. It is important to assess blue water footprint to understand the environmental impact of water consumption and to promote sustainable water management practices. Volume of surface and groundwater used from sources like rivers and aquifers.[9] This water is used for various purposes such as irrigation, industrial processes, and domestic consumption. Managing and reducing blue water footprint is important to ensure sustainable water use, and address water scarcity.

A green water footprint refers to the amount of water from precipitation that, after having been stored in the root zone of the soil (green water), is either lost by evapotranspiration or incorporated by plants. It is particularly relevant for agricultural, horticultural and forestry products.[6] Green water footprint is important for many different reasons. One being sustainable agriculture. Understanding the green water footprint helps in sustainable farming practices. According to “The Value of Rainwater: Why Green Water Footprints Matter.” by GRACE communications foundation, “Shifting precipitation patterns under climate change have changed the timing and amount of precipitation compared to the past. As this shift towards less predictable “drought and deluge” cycles occur, risks increase for farmers in terms of planning, planting and eventual harvests. Just because a given crop in a certain place or time depends more on irrigation and less on rainwater doesn’t mean it can survive without the rainwater.” [10] In the Article "Water Footprint and Why it is Important" by Rick LeBlanc it states as well "If coffee plants are not irrigated and rely on green water from rainfall, then they are utilizing water but not consuming it, as they would be if the water was being drawn from an aquifer or a body of water. It is important to consider the geographical and climatic context. Where there is abundant rainwater, the impact of water usage by the coffee plants on the ecosystem is minimal compared to more arid growing areas." [11] This demonstrates that while a plant can use water without the green water aspect, it cannot consume it. It will therefore become less healthy than if the green water from the rain had been used. Rainwater stored in soil and used for crop growth or ecosystems.[12] The volume of water from soil moisture consumed in the production process, primarily through agricultural activities. Green water footprint is essential mainly for the purpose of agriculture because without it, especially in dryer climates, it is almost impossible to create healthy crops.

A grey water footprint refers to the volume of water that is required to dilute pollutants (industrial discharges, seepage from tailing ponds at mining operations, untreated municipal wastewater, or nonpoint source pollution such as agricultural runoff or urban runoff) to such an extent that the quality of the water meets agreed water quality standards.[6] It is calculated as:

${\displaystyle {\frac {L}{c_{\text{max}}-c_{\text{nat}}}}}$

where L is the pollutant load (as mass flux), c_max the maximum allowable concentration and c_nat the natural concentration of the pollutant in the receiving water body (both expressed in mass/volume).[13]

Grey water is known as wastewater produced by everyday activities including bathing, cleaning dishes, and washing clothing. Understanding the environmental effects of our daily actions, such as water use and pollution, is made easier by looking at our grey water footprint. There are multiple benefits to including a grey water recycling system in homes. “Benefits of Greywater Recycling Systems” by Global Water Group of Companies states that, “ By reusing your household greywater, you are contributing to water conservation. Usage of tap water declines by 16-45 percent in households that reuse their greywater. Beyond your backyard, greywater can also be reused to become an additional source to existing water supplies in drought-stricken areas.” [14] Although there are benefits to including grey water recycling in everyday lives, there are also downsides to it. Grey water can also be considered a dangerous water footprint. According to “What is Gray water” by Friends of the Earth, it states “Gray water can lead to oxygen depletion and spread bacteria. It also leads to higher levels of nutrients in the ocean ecosystem which can result in toxic algal blooms and dead zones”.[15] This is why it is so important to manage this water footprint correctly. Freshwater volume required to assimilate pollutants in water bodies.[16] This category is particularly relevant when considering industrial waste or agricultural runoff. Being able to manage this footprint is crucial for minimizing pollution and optimizing water use in a sustainable and environmentally friendly manner.

According to “Water balance of global aquifers revealed by groundwater footprint” by Tom Gleeson, Yoshihide Wada, Marc F. P. Bierkens & Ludovicus P. H. van Beek, “Ground Water Footprint is the area required to sustain groundwater use and groundwater-dependent ecosystem services of a region of interest, such as an aquifer, watershed or community.” [7] It refers to the total amount of groundwater that is taken from aquifers to meet human needs. According to “Our Oversized Groundwater Footprint” by Sandra Postel, it is claimed that “the size of the global groundwater footprint – defined as the area required to sustain groundwater use and groundwater-dependent ecosystem services — is about 3.5 times the actual area of aquifers tapped for water supplies”.[17] This is showing the clear importance of groundwater footprint, but also how in demand it is as well. Majority of people rely on groundwater as their source of water and having enough aquifers along with keeping it sanitary is extremely important. "For example, water foot printing, provides quantitative evidence to indicate which water bodies are preferable for extracting or discharging water."[18] Is said in "The how and why of measuring your water footprint". by Adrian Johnson. This is further explaining how Ground Water footprint is more preferred as the way of extracting water, initiating how important it is to keep healthy. Due to the fact that most people around the world depend on groundwater, it is extremely important to keep the environment it is found in sanitary as well. “Without groundwater it can lead to things like reduced water levels in rivers and lakes and altered ecosystems”.[17] Managing the ground water footprint is extremely important to maintain long term water sustainability.

The water footprint of a process is expressed as volumetric flow rate of water. That of a product is the whole footprint (sum) of processes in its complete supply chain divided by the number of product units. For consumers, businesses and geographic area, water footprint is indicated as volume of water per time, in particular:[13]

• That of a consumer is the sum of footprint of all consumed products.
• That of a community or a nation is the sum for all of its members resp. inhabitants.
• That of a business is the footprint of all produced goods.
• That of a geographically delineated area is the footprint of all processes undertaken in this area. The virtual change in water of an area is the net import of virtual water V_{i, net}, defined as the difference of the gross import V_i of virtual water from its gross export V_e. The water footprint of national consumption WF_area,nat results from this as the sum of the water footprint of national area and its virtual change in water.

Databases and computing tools are very important for figuring out an individual's water footprint. However, specific equipment is essential for primary data collection such as:

• Flow Meters: Measures water usage across pipes.[19]
• Evapotranspiration Sensors: These are crucial for understanding water usage in agricultural activities.[20]

• Water Quality Test Kits and Analyzers: Instrumental in evaluating pollutant levels, thereby aiding in the estimation of the green water footprint.[21]
• Soil Moisture Sensors: Provide real-time data on soil water content, enhancing the accuracy of green water footprint assessments in agriculture.[22]

The Water Footprint Network is an international learning community (a non-profit foundation under Dutch law) which serves as a platform for sharing knowledge, tools and innovations among governments, businesses and communities concerned about growing water scarcity and increasing water pollution levels, and their impacts on people and nature. The network consists of around 100 partners from all sectors – producers, investors, suppliers and regulators – as well as non-governmental organisations and academics. It describes its mission as follows:

To provide science-based, practical solutions and strategic insights that empower companies, governments, individuals and small-scale producers to transform the way we use and share fresh water within earth's limits.[23]

In February 2011, the Water Footprint Network, in a global collaborative effort of environmental organizations, companies, research institutions and the UN, launched the Global Water Footprint Standard. In July 2014, the International Organization for Standardization issued ISO 14046:2014, Environmental management—Water footprint—Principles, requirements and guidelines, to provide practical guidance to practitioners from various backgrounds, such as large companies, public authorities, non-governmental organizations, academic and research groups as well as small and medium enterprises, for carrying out a water footprint assessment. The ISO standard is based on life-cycle assessment (LCA) principles and can be applied for different sorts of assessment of products and companies.[29]

Life-cycle assessment (LCA) is a systematic, phased approach to assessing the environmental aspects and potential impacts that are associated with a product, process or service. "Life cycle" refers to the major activities connected with the product's life-span, from its manufacture, use, and maintenance, to its final disposal, and also including the acquisition of raw material required to manufacture the product.[30] Thus a method for assessing the environmental impacts of freshwater consumption was developed. It specifically looks at the damage to three areas of protection: human health, ecosystem quality, and resources. The consideration of water consumption is crucial where water-intensive products (for example agricultural goods) are concerned that need to therefore undergo a life-cycle assessment.[31] In addition, regional assessments are equally as necessary as the impact of water use depends on its location. An LCA looks at a raw material from the time it is made, when it is used, and when it is thrown away or recycled. In short, LCA is important as it identifies the impact of water use in certain products, consumers, companies, nations, etc. which can help reduce the amount of water used.[32]

Globally, many water footprints lead to negative impacts such as pollution, over-abstraction of resources, and degradation of ecosystems. Hoekstra and Mekonnen observed that 50% of the UK's external blue water footprint is situated in river basins and aquifers with unsustainable water usage.[33] Studies have consistently found unsustainability in water use across our footprints, especially in relation to the production of food, clothing, and mining in the Global South.[34][35]

At the COP26 event in 2021, international attention was garnered towards the Glasgow Declaration for Fair Water Footprints. This was a step towards the environmental and socio-economic ramifications of water footprints.[36] This statement shows that the "Global South" is carrying too much of the environmental load to meet the needs of the "Global North's" consumption habits.[37]

The assessment of total water use in connection to consumption can be approached from both ends of the supply chain.[58] The water footprint of production estimates how much water from local sources is used or polluted in order to provide the goods and services produced in that country. The water footprint of consumption of a country looks at the amount of water used or polluted (locally, or in the case of imported goods, in other countries) in connection with all the goods and services that are consumed by the inhabitants of that country. The water footprint of production and that of consumption, can also be estimated for any administrative unit such as a city, province, river basin or the entire world.[1]

The absolute water footprint is the total sum of water footprints of all people. A country's per capita water footprint (that nation's water footprint divided by its number of inhabitants) can be used to compare its water footprint with those of other nations.

The global water footprint in the period 1996–2005 was 9.087 Gm³/yr (Billion Cubic Metres per year, or 9.087.000.000.000.000 liters/year), of which 74% was and green, 11% blue, 15% grey. This is an average amount per capita of 1.385 Gm³/yr., or 3.800 liters per person per day.[59] On average 92% of this is embedded in agricultural products consumed, 4.4% in industrial products consumed, and 3.6% is domestic water use. The global water footprint related to producing goods for export is 1.762 Gm³/y.[60]

In absolute terms, India is the country with the largest water footprint in the world, a total of 987 Gm³/yr. In relative terms (i.e. taking population size into account), the people of the USA have the largest water footprint, with 2480 m³/yr per capita, followed by the people in south European countries such as Greece, Italy and Spain (2300–2400 m³/yr per capita). High water footprints can also be found in Malaysia and Thailand. In contrast, the Chinese people have a relatively low per capita water footprint with an average of 700 m³/yr.[1] (These numbers are also from the period 1996-2005.)

Global average numbers and composition of all national water footprints, internal and external

The internal water footprint is the amount of water used from domestic water resources; the external water footprint is the amount of water used in other countries to produce goods and services imported and consumed by the inhabitants of the country. When assessing the water footprint of a nation, it is crucial to take into account the international flows of virtual water (also called embodied water, i.e. the water used or polluted in connection to all agricultural and industrial commodities) leaving and entering the country. When taking the use of domestic water resources as a starting point for calculating a nation's water footprint, one should subtract the virtual water flows that leave the country and add the virtual water flows that enter the country.[1]

The external part of a nation's water footprint varies strongly from country to country. Some African nations, such as Sudan, Mali, Nigeria, Ethiopia, Malawi and Chad have hardly any external water footprint, simply because they have little import. Some European countries on the other hand—e.g. Italy, Germany, the UK and the Netherlands—have external water footprints that constitute 50–80% of their total water footprint. The agricultural products that on average contribute most to the external water footprints of nations are: bovine meat, soybean, wheat, cocoa, rice, cotton and maize.[1]

The top 10 gross virtual water exporting nations, which together account for more than half of the global virtual water export, are the United States (314 Gm³/year), China (143 Gm³/year), India (125 Gm³/year), Brazil (112 Gm³/year), Argentina (98 Gm³/year), Canada (91 Gm³/year), Australia (89 Gm³/year), Indonesia (72 Gm³/year), France (65 Gm³/year), and Germany (64 Gm³/year).[60]

The top 10 gross virtual water importing nations are the United States (234 Gm³/year), Japan (127 Gm³/year), Germany (125 Gm³/year), China (121 Gm³/year), Italy (101 Gm³/year), Mexico (92 Gm³/year), France (78 Gm³/year), the United Kingdom (77 Gm³/year), and The Netherlands (71 Gm³/year).[60]

Each EU citizen consumes 4,815 litres of water per day on average; 44% is used in power production primarily to cool thermal plants or nuclear power plants. Energy production annual water consumption in the EU 27 in 2011 was, in billion m³: for gas 0.53, coal 1.54 and nuclear 2.44. Wind energy avoided the use of 387 million cubic metres (mn m³) of water in 2012, avoiding a cost of €743 million.[62][63]

In south India the state Tamil Nadu is one of the main agricultural producers in India and it relies largely in groundwater for irrigation. In ten years, from 2002 to 2012, the Gravity Recovery and Climate Experiment calculated that the groundwater reduced in 1.4 m yr−1, which "is nearly 8% more than the annual recharge rate."[46]

According to Dennis Wichelns of the International Water Management Institute: "Although one goal of virtual water analysis is to describe opportunities for improving water security, there is almost no mention of the potential impacts of the prescriptions arising from that analysis on farm households in industrialized or developing countries. It is essential to consider more carefully the inherent flaws in the virtual water and water footprint perspectives, particularly when seeking guidance regarding policy decisions."[65]

The application and interpretation of water footprints may sometimes be used to promote industrial activities that lead to facile criticism of certain products. For example, the 140 litres required for coffee production for one cup[2] might be of no harm to water resources if its cultivation occurs mainly in humid areas, but could be damaging in more arid regions. Other factors such as hydrology, climate, geology, topography, population and demographics should also be taken into account. Nevertheless, high water footprint calculations do suggest that environmental concern may be appropriate.

Many of the criticisms, including the above ones, compare the description of the water footprint of a water system to generated impacts, which is about its performance. Such a comparison between descriptive and performance factors and indicators is basically flawed.[66]

The use of the term footprint can also confuse people familiar with the notion of a carbon footprint, because the water footprint concept includes sums of water quantities without necessarily evaluating related impacts. This is in contrast to the carbon footprint, where carbon emissions are not simply summarized but normalized by CO₂ emissions, which are globally identical, to account for the environmental harm. The difference is due to the somewhat more complex nature of water; while involved in the global hydrological cycle, it is expressed in conditions both local and regional through various forms like river basins, watersheds, on down to groundwater (as part of larger aquifer systems). Furthermore, looking at the definition of the footprint itself, and comparing ecological footprint, carbon footprint and water footprint, we realize that the three terms are indeed legitimate.[66]

Water footprint accounting has advanced substantially in recent years, however, water footprint analysis also needs sustainability assessment as its last phase.[28] One of the developments is to employ sustainable efficiency and equity ("Sefficiency in Sequity"), which present a comprehensive approach to assessing the sustainable use of water.[66][70]