Multiple Ways of Assessing Threats to Water: Supply-Side and Demand-Side Problems
Newsweek cover, 2010: echoing famous T. Boone Pickens quote
- There are both supply-side threats and demand-side threats to water necessary to meet human needs; as T. Boone Pickens has been quoted as saying, "Water is the new oil"
- One supply-side threat arises from instances in which we are withdrawing freshwater from surface water sources and groundwater aquifers at rates faster than replenishment or recharge
- Another supply-side problem is that even if there is enough water, it is not water that is good enough to meet human needs; much of the world's fresh water is being degraded
- Still another supply-side problem is the fact that distinct from physical water scarcity, there is economic scarcity for the global poor
- One demand-side concern arises from the fact of an increasing number of people on the planet
- Another demand-side problem is that high-demand users sometimes are geographically concentrated in regions that cannot sustain demand levels
- Still another demand-side problem arises from technologies that waste more water than alternative technologies
- A fourth set of demand-side problems is that demand is often insufficiently restrained because of inadequate price mechanisms and outdated legal rules that set few limits on excessive use
For some detailed general news coverage of water issues, see the 2010 Newsweek story (cover shown in the graphic above), as well as a special issue of National Geographic Magazine in 2010 devoted to a wide range of water issues.
FAO Video: Water 101 - Global Water Scarcity Trends:
For a great source for more details regarding the causes and projected consequences of the global water crisis, see the UN Water's 2011 Policy Brief
- By 2025, 1.8 billion people will experience absolute water scarcity, and 2/3 of the world will be living under water-stressed conditions
- Scarcity can take two forms: there is an important distinction drawn in this discussion between Physical Water Scarcity and Economic Water Scarcity
- By 2030, almost half the world will live under conditions of high water stress
For a great source for more details regarding the causes and projected consequences of the global water crisis, see the UN Water's 2011 Policy Brief
Some Basics of Water Availability: Saltwater, Freshwater, Groundwater, and Surface Water
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One of the more frequently cited statistics in discussions of water availability is the fact that only around 2.5% of the Earth's water is freshwater. The overwhelming amount of water is saline or salt water, mostly found in the oceans.
Of the 2.5% of freshwater available for the support of human life, agriculture, and most forms of non-ocean life, 30.1% is groundwater. Groundwater is the water stored deep beneath the Earth's surface in underground aquifers. Another 68.6% of all freshwater is stored in glaciers and polar caps. That leaves only 1.3% of the total freshwater on Earth is in surface water sources such as lakes, rivers, and streams. But it is surface water humans and other species rely upon for their biological needs.
Even the bulk of surface water on Earth is found in snow and ice - approximately 73.1%. Surface water found in lakes, rivers and streams accounts for just over another 20%.
And yet, when we (humans) think about our needs for water we spend most of our time thinking about the surface water found in lakes and rivers and the vast watersheds within which they and their tributaries are found. It is on the basis of a consideration of such a narrow set of all freshwater resources that we plan the location of our cities, derive most of our drinking water, build waterways for transporting people and goods, pipe vast quantities very long distances for agricultural purposes (e.g., from Lake Mead to the California Central Valley), and worry most focally about whenever we do pause to worry about water pollution and water-related environmental degradation.
Graphic Source: Igor Shiklomanov's chapter "World fresh water resources" in Peter H. Gleick (editor), 1993, Water in Crisis: A Guide to the World's Fresh Water Resources (Oxford University Press, New York). A detailed discussion of these and many more elementary aspects of the hydrologic cycle can be found at the website for the US Geological Service, where this graphic was found.
Of the 2.5% of freshwater available for the support of human life, agriculture, and most forms of non-ocean life, 30.1% is groundwater. Groundwater is the water stored deep beneath the Earth's surface in underground aquifers. Another 68.6% of all freshwater is stored in glaciers and polar caps. That leaves only 1.3% of the total freshwater on Earth is in surface water sources such as lakes, rivers, and streams. But it is surface water humans and other species rely upon for their biological needs.
Even the bulk of surface water on Earth is found in snow and ice - approximately 73.1%. Surface water found in lakes, rivers and streams accounts for just over another 20%.
And yet, when we (humans) think about our needs for water we spend most of our time thinking about the surface water found in lakes and rivers and the vast watersheds within which they and their tributaries are found. It is on the basis of a consideration of such a narrow set of all freshwater resources that we plan the location of our cities, derive most of our drinking water, build waterways for transporting people and goods, pipe vast quantities very long distances for agricultural purposes (e.g., from Lake Mead to the California Central Valley), and worry most focally about whenever we do pause to worry about water pollution and water-related environmental degradation.
Graphic Source: Igor Shiklomanov's chapter "World fresh water resources" in Peter H. Gleick (editor), 1993, Water in Crisis: A Guide to the World's Fresh Water Resources (Oxford University Press, New York). A detailed discussion of these and many more elementary aspects of the hydrologic cycle can be found at the website for the US Geological Service, where this graphic was found.
Ground Water and Two Big Threats from the Disruption of the Hydrologic Cycle
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Groundwater is the hidden resource behind what is visible in any ordinary landscape. Groundwater located in shallow and deep aquifers feeds the lakes and streams. Rainwater infiltrates the subsoil and replenishes groundwater supplies. Just how much replenishment of aquifers within the normal operation of the hydrologic cycle depends on a number of variables. Some precipitation evaporates, especially under arid and hot conditions. Some water flows into streams and rivers but does not infiltrate deeply. It becomes runoff that moves directly into the ocean, taking a greater part of the available water from the hydrologic cycle that might have remained within the stock of available freshwater.
Two major sources of disruption of the hydrological cycle are warming produced by climate change and features of the "built environment" that induce more runoff.
Two major sources of disruption of the hydrological cycle are warming produced by climate change and features of the "built environment" that induce more runoff.
- When climate change results in hotter, more arid surface conditions it prevents both infiltration needed for replenishment of deep reserves and reduces the surface water available for immediate uses such as agriculture or filling reservoirs for drinking water.
- Changes in the built environment, such as the creation of mass concentrations of "hardscape" - asphalt and concrete - as well as the destruction of watershed timberlands, marshes, and wetlands, ease the path for more rapid runoff such that more rainfall end up going straight to the sea.
FAO Map of Current Sites of Physical and Economic Water Scarcity
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Things are changing globally. On the one hand, there is good news. As the discusion below on the 7th Millenium Goal indicates, fewer people globally lack access to potable water than they did 30 years ago. Indeed, the percentage was cut in half. On the other hand, long term trends are not encouraging.
Among the important facts emphasized by the Food and Agriculture Organization (FAO) are these two:
Source: Food and Agriculture Organization of the United Nations (FAO) and UN-Water
Among the important facts emphasized by the Food and Agriculture Organization (FAO) are these two:
- Water use has been growing at more than the rate twice of population increase in the last century.
- By 2025, 1.8 Billion people will be living in countries or regions with absolute water scarcity, and two-thirds of the world population could be under stress conditions.
Source: Food and Agriculture Organization of the United Nations (FAO) and UN-Water
Progress Toward Millennium Development Goal 7: halving the proportion of the population without sustainable access to safe drinking water and basic sanitation
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The most recent WHO/UNICEF Joint Monitoring Programme for Water Supply and Sanitation (JMP) biennial report on the progress towards the drinking-water and sanitation target under Millennium Development Goal 7 - halving the proportion of the population without sustainable access to safe drinking water and basic sanitation between 1990 and 2015 - . was met in 2010, five years ahead of schedule. However, an estimated 780 million still lacked safe drinking water in 2010, and the world is unlikely to meet the MDG sanitation target.
While there is much good news in this 2012 report, the fact remains that severe water stress affecting 1/3 of the world's population is expected to double to 2/3 by 2025. (See FAO data above in their Water 101 video and the other trend projection maps above).
While there is much good news in this 2012 report, the fact remains that severe water stress affecting 1/3 of the world's population is expected to double to 2/3 by 2025. (See FAO data above in their Water 101 video and the other trend projection maps above).
It's Important to Know Where Rates of Use Will Exceed Rates of Recharge
Some key facts and projections are available from the UNWater.org webpage where important statistics and maps from various sources are collected:
- Water withdrawals are predicted to increase by 50 percent by 2025 in developing countries, and 18 per cent in developed countries. (Source: Global Environment Outlook: environment for development (GEO-4) )
- Over 1.4 billion people currently live in river basins where the use of water exceeds minimum recharge levels, leading to the desiccation of rivers and depletion of groundwater. (Source: Human Development Report 2006)
- In 60 percent of European cities with more than 100,000 people, groundwater is being used at a faster rate than it can be replenished. (Source: World Business Council For Sustainable Development (WBCSD))
- The role of agriculture, both as a source of groundwater depletion due to water-intensity farming and animal husbandry techniques and as an object of special concern as water access becomes more difficult in some regions, will be an important part of the evolving global story about water resource supply and distribution.
Climate Change Will Disproportionately Affect Regions that Depend on Rainwater for Agriculture
The consensus is that there will be more or less the same aggregate available water resources in 2050 as there was in 2007, but there will be far more people on the planet. As the maps projecting through 2025 indicate, the reduced availability of freshwater for all uses will not be distributed equally across the globe.
The main areas to face greater losses are the Equatorial regions, which are already among the most water stressed areas. These areas tend to be the parts of the world most dependent on rainfall rather than irrigation as the basis for agriculture. Rain dependent agricultural areas are at much greater risk of crop failure. They are among the least productive farmlands in the world. According to the FAO, irrigation increases yields of most crops by 100 to 400 percent, and irrigated agriculture currently contributes to 40 percent of the world's food production. The hottest, driest regions of the world, then, are already at a significant disadvantage in the efforts to meet their own food needs, but even as early as 2020, the Intergovernmental Panel on Climate Change predicts yields from rain-dependent agriculture could be down by 50 percent. (Source: Unwater.org).
The main areas to face greater losses are the Equatorial regions, which are already among the most water stressed areas. These areas tend to be the parts of the world most dependent on rainfall rather than irrigation as the basis for agriculture. Rain dependent agricultural areas are at much greater risk of crop failure. They are among the least productive farmlands in the world. According to the FAO, irrigation increases yields of most crops by 100 to 400 percent, and irrigated agriculture currently contributes to 40 percent of the world's food production. The hottest, driest regions of the world, then, are already at a significant disadvantage in the efforts to meet their own food needs, but even as early as 2020, the Intergovernmental Panel on Climate Change predicts yields from rain-dependent agriculture could be down by 50 percent. (Source: Unwater.org).
Map of Projected Physical and Economic Water Scarcity in 2025
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- Discussions of water scarcity, water stress, or other ways of accounting for future challenges are not as straightforward as they might appear. The distinction between economic and physical scarcity is one important factor to keep in mind. Here are some other important observations by Frank R. Rijsberman of the International Water Management Institute:
- "What is water scarcity? When an individual does not have access to safe and affordable water to satisfy her or his needs for drinking, washing or their livelihoods we call that person water insecure. When a large number of people in an area are water insecure for a significant period of time, then we can call that area water scarce. It is important to note, however, that there is no commonly accepted definition of water scarcity. Whether an area qualifies as “water scarce” depends on, for instance: a) how people’s needs are defined – and whether the needs of the environment, the water for nature, are taken into account in that definition; b) what fraction of the resource is made available, or could be made available, to satisfy these needs; c) the temporal and spatial scales used to define scarcity."
Another Map Showing Additional Information Regarding Vulnerabilities
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The UN's website on the global water outlook makes the following two claims:
- "Water scarcity is among the main problems to be faced by many societies and the World in the XXIst century. Water use has been growing at more than twice the rate of population increase in the last century, and, although there is no global water scarcity as such, an increasing number of regions are chronically short of water."
- "Water scarcity is both a natural and a human-made phenomenon. There is enough freshwater on the planet for six billion people but it is distributed unevenly and too much of it is wasted, polluted and unsustainably managed."
Source: Vital Water Graphics. UNEP
Global Trends in Groundwater Depletion
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A 2012 study of global groundwater depletion published in Nature demonstrates how some of the planet's largest underground aquifers are now being depleted by irrigation and other uses faster than they can be replenished by rainwater. The Abstract of the paper, "Water balance of global aquifers revealed by groundwater footprint," summarizes the key finding:
"Most assessments of global water resources have focused on surface water, but unsustainable depletion of groundwater has recently been documented on both regional and global scales. It remains unclear how the rate of global groundwater depletion compares to the rate of natural renewal and the supply needed to support ecosystems. Here we define the groundwater footprint (the area required to sustain groundwater use and groundwater-dependent ecosystem services) and show that humans are overexploiting groundwater in many large aquifers that are critical to agriculture, especially in Asia and North America. We estimate that the size of the global groundwater footprint is currently about 3.5 times the actual area of aquifers and that about 1.7 billion people live in areas where groundwater resources and/or groundwater-dependent ecosystems are under threat. That said, 80 per cent of aquifers have a groundwater footprint that is less than their area, meaning that the net global value is driven by a few heavily overexploited aquifers."
The map compares the usage footprint in each of these key areas with the actual rainfall the aquifer gets. The orange and red areas are areas of overexploitation, while the blue areas show where there is more rainfall replenishment than water uptake by humans.
"Most assessments of global water resources have focused on surface water, but unsustainable depletion of groundwater has recently been documented on both regional and global scales. It remains unclear how the rate of global groundwater depletion compares to the rate of natural renewal and the supply needed to support ecosystems. Here we define the groundwater footprint (the area required to sustain groundwater use and groundwater-dependent ecosystem services) and show that humans are overexploiting groundwater in many large aquifers that are critical to agriculture, especially in Asia and North America. We estimate that the size of the global groundwater footprint is currently about 3.5 times the actual area of aquifers and that about 1.7 billion people live in areas where groundwater resources and/or groundwater-dependent ecosystems are under threat. That said, 80 per cent of aquifers have a groundwater footprint that is less than their area, meaning that the net global value is driven by a few heavily overexploited aquifers."
The map compares the usage footprint in each of these key areas with the actual rainfall the aquifer gets. The orange and red areas are areas of overexploitation, while the blue areas show where there is more rainfall replenishment than water uptake by humans.
Where Does All the Water Go?
Our modern industrial system of agriculture poses still further challenges both because of its impact on our ability to meet our needs for freshwater and because it is in itself an increasingly carbon-intensive enterprise. The use of fertilizers and pesticides that has been largely responsible for the massive increase in yield per acre since WWII, but it requires far more water per acre than traditional forms of agriculture.
The FAO estimates that 70% of the world's water is used for agricultural purposes. The graphic on the right shows that it takes approximately 15,000 litres of water to produce one kilogram of meat. That compares to approximately 1,500 litres to produce a kilogram of wheat. Approximately 3,000 litres per day are needed to satisfy a person's daily nutritional needs - that estimate, of course, depends on the foods that are used to meet those needs.
One recent study suggests that in some places energy production may be overtaking agriculture as the primary user of water. Burning Our Rivers: The Water Footprint of Electricity, a 2012 report by River Network attempts to summarize what is known about the water footprint of various modes of electrical power production. Here are some of their findings in the US setting. One striking conclusion is that in the US "electricity production by coal, nuclear and natural gas power plants is the fastest-growing use of freshwater in the U.S., accounting for more than about ½ of all fresh, surface water withdrawals from rivers and lakes. This is more than any other economic sector, including agriculture."
The FAO estimates that 70% of the world's water is used for agricultural purposes. The graphic on the right shows that it takes approximately 15,000 litres of water to produce one kilogram of meat. That compares to approximately 1,500 litres to produce a kilogram of wheat. Approximately 3,000 litres per day are needed to satisfy a person's daily nutritional needs - that estimate, of course, depends on the foods that are used to meet those needs.
One recent study suggests that in some places energy production may be overtaking agriculture as the primary user of water. Burning Our Rivers: The Water Footprint of Electricity, a 2012 report by River Network attempts to summarize what is known about the water footprint of various modes of electrical power production. Here are some of their findings in the US setting. One striking conclusion is that in the US "electricity production by coal, nuclear and natural gas power plants is the fastest-growing use of freshwater in the U.S., accounting for more than about ½ of all fresh, surface water withdrawals from rivers and lakes. This is more than any other economic sector, including agriculture."
"VIrtual Water" Adjustments to National Per Capita Water Footprint Estimates
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A 2012 study by Hoekstra and Mekonnen takes a comprehensive look at the global water footprint (WF) by nations. It examines first the consumptive use of rainwater (green WF) and ground and surface water (blue WF) and volumes of water polluted (gray WF). Among the findings of the study, are estimates of the largest components of water consumption: e.g., "cereal products gives the largest contribution to the WF of the average consumer (27%), followed by meat (22%) and milk products (7%). The volume and pattern of consumption and the WF per ton of product of the products consumed are the main factors determining the WF of a consumer."
But one of the key points made in the study is that the national average per capita WF can be estimated from both a production and consumption perspective. The difference lies in the fact that international "virtual water" flows are estimated based on trade in agricultural and industrial commodities. About one-fifth of the global WF involves production for export. The graphic from the paper published in the Proceedings of the National Academy of Sciences (PNAS), provides a spatial analysis of water consumption and pollution based on worldwide trade indicators, demographic data and water-usage statistics.
The significance of virtual water cannot be underemphasized. Some countries assessed from a water production perspective initially apear to use less water per capita, but that number increases once virtual water is included, for example the water consumed in one nation but "produced" in another nation and exported in the form of agricultural products. As the authors note, "The study illustrates the global dimension of water consumption and pollution by showing that several countries heavily rely on foreign water resources and that many countries have significant impacts on water consumption and pollution elsewhere." So, for example, a significant amount of the water consumption that would show up in China's column, if data are not adjusted to reflect the ultimate locus of consumption, shows up in the US column once the adjustment is made for virtual water. In effect, some countries "offshore" water overdraft and pollution by consuming products from international trade.
But one of the key points made in the study is that the national average per capita WF can be estimated from both a production and consumption perspective. The difference lies in the fact that international "virtual water" flows are estimated based on trade in agricultural and industrial commodities. About one-fifth of the global WF involves production for export. The graphic from the paper published in the Proceedings of the National Academy of Sciences (PNAS), provides a spatial analysis of water consumption and pollution based on worldwide trade indicators, demographic data and water-usage statistics.
The significance of virtual water cannot be underemphasized. Some countries assessed from a water production perspective initially apear to use less water per capita, but that number increases once virtual water is included, for example the water consumed in one nation but "produced" in another nation and exported in the form of agricultural products. As the authors note, "The study illustrates the global dimension of water consumption and pollution by showing that several countries heavily rely on foreign water resources and that many countries have significant impacts on water consumption and pollution elsewhere." So, for example, a significant amount of the water consumption that would show up in China's column, if data are not adjusted to reflect the ultimate locus of consumption, shows up in the US column once the adjustment is made for virtual water. In effect, some countries "offshore" water overdraft and pollution by consuming products from international trade.
The Components of the Water Footprint and the Impact of Biofuels
The way we measure the water footprint of various crops depends on certain assumptions regarding what it actually means when we say some crop requires some amount of water. Not all agricultural uses of water are created equal. Some uses badly degrade the water while others do little or no enduring damage. A study of the impact on water from 12 biofuels reveals some significant differences among them.
The authors of the study draw an important set of distinctions among three types of water footprint (WF):
"The WF consists of 3 components: the green WF, the blue WF, and the gray WF. The green WF refers to rainwater that evaporated during production, mainly during crop growth. The blue WF refers to surface and groundwater for irrigation evaporated during crop growth. The gray WF is the volume of water that becomes polluted during production, defined as the amount of water needed to dilute pollutants discharged into the natural water system to the extent that the quality of the ambient water remains above agreed water quality standards.”
The chart from the paper appearing in the Proceedings of the National Academy of Sciences shows the comparative blue and green water impact of the major biofuels in global production. The results of the study are reported in cubic meters per giga-Joule of energy produced (m3/GJ). In more familiar terms, a liter of ethanol made from sugar beets uses "just" 1,400 litres of water, while rapeseed or soya required 14,000 liters of water to make just one liter of biodiesel.
Studies of US biofuel water footprints yield results in line with the global weighted averages reported in the National Academy study, but an important benchmark for comparison is how they stack up against biofuels grown in the US. For example, a 2010 study in Biofuels estimated the water requirements for various feedstocks range from approximately 500 to 2000 liters of water per liter of ethanol (corn-based) produced compared to approximately 1000 to 4000 liters of water for soybeans per ethanol-equivalent liter of biodiesel produced.
For purposes of comparison, The FAO estimates that on average globally it takes approximately 15,000 liters of water to produce one kilogram of meat. That compares to approximately 1,500 liters to produce a kilogram of wheat.
The authors of the study draw an important set of distinctions among three types of water footprint (WF):
"The WF consists of 3 components: the green WF, the blue WF, and the gray WF. The green WF refers to rainwater that evaporated during production, mainly during crop growth. The blue WF refers to surface and groundwater for irrigation evaporated during crop growth. The gray WF is the volume of water that becomes polluted during production, defined as the amount of water needed to dilute pollutants discharged into the natural water system to the extent that the quality of the ambient water remains above agreed water quality standards.”
The chart from the paper appearing in the Proceedings of the National Academy of Sciences shows the comparative blue and green water impact of the major biofuels in global production. The results of the study are reported in cubic meters per giga-Joule of energy produced (m3/GJ). In more familiar terms, a liter of ethanol made from sugar beets uses "just" 1,400 litres of water, while rapeseed or soya required 14,000 liters of water to make just one liter of biodiesel.
Studies of US biofuel water footprints yield results in line with the global weighted averages reported in the National Academy study, but an important benchmark for comparison is how they stack up against biofuels grown in the US. For example, a 2010 study in Biofuels estimated the water requirements for various feedstocks range from approximately 500 to 2000 liters of water per liter of ethanol (corn-based) produced compared to approximately 1000 to 4000 liters of water for soybeans per ethanol-equivalent liter of biodiesel produced.
For purposes of comparison, The FAO estimates that on average globally it takes approximately 15,000 liters of water to produce one kilogram of meat. That compares to approximately 1,500 liters to produce a kilogram of wheat.
Water.org: A Source for Key Water Facts
Water.org is a nonprofit organization devoted to providing equitable access to safe water and sanitation throughout the developing world. Its featured projects span three continents from Haiti to Ethiopia to India, focusing on improving livelihoods for the poorest, most marginalized communities. These projects follow a time-tested formula based on community ownership, appropriate technology, and measurement of results. Of particular interest is the WaterCredit program, which seeks to utilize microfinance as a tool towards greater improvements in water and sanitation.
As an educational tool, Water.org provides an overarching analysis of water facts that outline the global crisis, including a more specific focus on the special status and considerations for women in affected societies. The website also boasts visually-striking breakdowns of water facts related to children, disease, and economics, among other topics. The site also provides a very useful list of other web resources.
As an educational tool, Water.org provides an overarching analysis of water facts that outline the global crisis, including a more specific focus on the special status and considerations for women in affected societies. The website also boasts visually-striking breakdowns of water facts related to children, disease, and economics, among other topics. The site also provides a very useful list of other web resources.