Peak water is a concept that underlines the growing constraints on the availability, quality, and use of freshwater resources. Peak water was defined in 2010 by Peter Gleick and Meena Palaniappan. They distinguish between peak renewable, peak non-renewable, and peak ecological water to demonstrate the fact that although there is a vast amount of water on the planet, sustainably managed water is becoming scarce.
Lester R. Brown, president of the Earth Policy Institute, wrote in 2013 that although there was extensive literature on peak oil, it was peak water that is "the real threat to our future". An assessment was published in August 2011 in the Stockholm International Water Institute's journal. Much of the world's water in underground aquifers and in lakes can be depleted and thus resembles a finite resource. The phrase peak water sparks debates similar to those about peak oil. In 2010, New York Times chose "peak water" as one of its 33 "Words of the Year".
There are concerns about impending peak water in several areas around the world: Peak ecological water, where ecological and environmental constraints are overwhelming the economic benefits provided by water use Peak non-renewable water, where groundwater aquifers are being overpumped (or contaminated) faster than nature recharges them (this example is most like the peak oil debate) Peak renewable water, where entire renewable flows are being consumed for human use If present trends continue, 1.8 billion people will be living with absolute water scarcity by 2025, and two-thirds of the world could be subject to water stress. Ultimately, peak water is not about running out of freshwater, but about reaching physical, economic, and environmental limits on meeting human demands for water and the subsequent decline of water availability and use.
Comparison with peak oil
The Hubbert curve has become popular in the scientific community for predicting the depletion of various natural resources. M. King Hubbert created this measurement device in 1956 for a variety of finite resources such as coal, oil, natural gas and uranium. Hubbert's curve was not applied to resources such as water originally, since water is a renewable resource. Some forms of water, however, such as fossil water, exhibit similar characteristics to oil, and overpumping (faster than the rate of natural recharge of groundwater) can theoretically result in a Hubbert-type peak. A modified Hubbert curve applies to any resource that can be harvested faster than it can be replaced. Like peak oil, peak water is inevitable given the rate of extraction of certain water systems. A current argument is that growing populations and demands for water will inevitably lead to non-renewable use of water resources.
Water supply
Fresh water is a renewable resource, yet the world's supply of clean, fresh water is under increasing demand for human activities.Forecast of water usage as a percentage of renewable water resources broken down by World Bank regions from International Futures The world has an estimated 1.34 billion cubic kilometers of water, but 96.5% of it is salty. Almost 70% of fresh water can be found in the ice caps of Antarctica and Greenland. Less than 1% of this water on Earth is accessible to humans, the rest is contained in soil moisture or deep underground. Accessible freshwater is located in lakes, rivers, reservoirs and shallow underground sources. Rainwater and snowfall do very little to replenish many underground sources.
+Freshwater sources (top 15 countries) Total freshwater supply Country (km3/yr) Year 2000 2011 1985 2011 2008 2000 2011 2000 2011 2001 2000 1999 2011 2000 2011
The amount of available freshwater supply in some regions is decreasing because of (i) climate change, which has caused receding glaciers, reduced stream and river flow, and shrinking lakes; (ii) contamination of water by human and industrial wastes; and (iii) overuse of non-renewable groundwater aquifers. Many aquifers have been over-pumped and are not recharging quickly. Although the total freshwater supply is not used up, much has become polluted, salted, unsuitable or otherwise unavailable for drinking, industry, and agriculture.
Water demand Water demand already exceeds supply in many parts of the world, and as the world population continues to rise, many more areas are expected to experience this imbalance in the near future.
Agriculture represents 70% of freshwater use worldwide.
Agriculture, industrialization and urbanization all serve to increase water consumption.
Freshwater withdrawal by country The largest total use of water comes from India, China and the United States, countries with large populations, extensive agricultural irrigation, and demand for food. See the following table:
+Freshwater withdrawal by country and sector (top 20 countries) Country Total freshwater withdrawal (km3/yr) Per capita withdrawal (m3/p/yr) Domestic use (m3/p/yr)(in %) Industrial use (m3/p/yr)(in %) Agricultural use (m3/p/yr)(in %) 761 627 46 (7%) 14 (2%) 567 (90%) 578.9 425 52 (12%) 99 (23%) 272 (64%) 482.2 1,518 193 (13%) 699 (46%) 626 (41%) 183.5 993 52 (5%) 8 (1%) 933 (94%) 113.3 487 58 (12%) 34 (7%) 400 (82%) 93.3 1,243 85 (7%) 12 (1%) 1143 (92%) 90 709 135 (19%) 127 (18%) 446 (63%) 82 921 9 (1%) 37 (4%) 875 (95%) 80.4 727 102 (14%) 67 (9%) 557 (77%) 76.68 546 109 (20%) 328 (60%) 109 (20%) 68.3 923 74 (8%) 55 (6%) 794 (86%) 66 2,097 147 (7%) 315 (15%) 1657 (79%) 59.84 2,782 445 (16%) 306 (11%) 2058 (74%) 58.07 297 83 (28%) 52 (17%) 162 (55%) 57.31 841 40 (5%) 41 (5%) 760 (90%) 56 2,015 141 (7%) 60 (3%) 1813 (90%) 45.4 755 151 (20%) 272 (36%) 332 (44%) 45.08 1,330 260 (20%) 913 (69%) 157 (12%) 40.1 530 74 (15%) 58 (11%) 393 (74%) 35.87 253 25 (10%) 5 (2%) 222 (88%)
India
India, the world's most populous country, has 20 percent of the Earth's population, but only four percent of its water. Water tables are dropping rapidly in some of India's main agricultural areas.
India has the largest water withdrawal out of all the countries in the world. Eighty-six percent of that water supports agriculture. That heavy use is dictated in large part by what people eat. People in India consume a lot of rice. Rice farmers in India typically get less than half the yield per unit area while using ten times more water than their Chinese counterparts. Economic development can make things worse because as people's living standards rise, they tend to eat more meat, which requires much water to produce. Growing a tonne of grain requires 1,000 tonnes of water; producing a tonne of beef requires 15,000 tonnes. To make a single hamburger requires around 4,940 liters (1,300 gallons) of water. To produce a glass of orange juice requires 850 liters (225 gallons) of freshwater.
China
China, the world's second most populous country, has the second largest water withdrawal; 68% supports agriculture while its growing industrial base consumes 26%. China is facing a water crisis where water resources are overallocated, used inefficiently, and severely polluted by human and industrial wastes. One-third of China's population lacks access to safe drinking water. Rivers and lakes are dead and dying, groundwater aquifers are over-pumped, uncounted species of aquatic life have been driven to extinction, and direct adverse impacts on both human and ecosystem health are widespread and growing.
In western China's Qinghai, through which the Yellow River’s main stream flows, more than 2,000 lakes have disappeared over the last 20 years. There were once 4,077 lakes. Global climate change is responsible for the reduction in flow of the (Huang He) Yellow River over the past several decades. The source of the Yellow River is the Qinghai-Xizang Tibetan Plateau where the glaciers are receding sharply.
In Hebei, which surrounds Beijing, the situation is much worse. Hebei is one of China's major wheat and corn growing provinces. The water tables have been falling fast throughout Hebei. The region has lost 969 of its 1,052 lakes. About 500,000 people are affected by a shortage of drinking water due to continuing droughts. Hydro-power generation is also impacted. Beijing and Tianjin depend on Hebei Province to supply their water from the Yangtze River. Beijing gets its water via the newly constructed South-North Water Transfer Project. The river originates in a glacier on the eastern part of the Tibetan Plateau.
United States
The United States has about 5% of the world's population, yet it uses almost as much water as India (~1/5 of world) or China (1/5 of world) because substantial amounts of water are used to grow food exported to the rest of the world. The United States agricultural sector consumes more water than the industrial sector, though substantial quantities of water are withdrawn (but not consumed) for power plant cooling systems. 40 out of 50 state water managers expect some degree of water stress in their state in the next 10 years.
The Ogallala Aquifer in the southern high plains (Texas and New Mexico) is being mined at a rate that far exceeds replenishment—a classic example of peak non-renewable water. Portions of the aquifer will not naturally recharge due to layers of clay between the surface and the water-bearing formation, and because rainfall rates simply do not match rates of extraction for irrigation. The term fossil water is sometimes used to describe water in aquifers that was stored over centuries to millennia. Use of this water is not sustainable when the recharge rate is slower than the rate of groundwater extraction.
In California, large amounts of groundwater are also being withdrawn from Central Valley groundwater aquifers. California's Central Valley is home to one-sixth of all irrigated land in the United States, and the state leads the nation in agricultural production and exports. The inability to sustain groundwater withdrawals over time may lead to adverse impacts on the region's agricultural productivity.
The Central Arizona Project (CAP) is a long canal that diverts a year from the Colorado River to irrigate more than of farmland. The CAP project also provides drinking water for Phoenix and Tucson. In 2008 it was estimated that Lake Mead, which dams the Colorado, had a 50-50 chance of running dry by 2021.
The Ipswich River near Boston now runs dry in some years due to heavy pumping of groundwater for irrigation. Maryland, Virginia and the District of Columbia have been fighting over the Potomac River. In drought years like 1999 or 2003, and on hot summer days the region consumes up to 85 percent of the river's flow.
Per capita withdrawal of water
Turkmenistan, Australia and Guyana use the most water per capita. See the table below:
+Freshwater withdrawal by country and sector (top 15 countries, per capita) Per capita withdrawal Total freshwater withdrawal Domestic use Industrial use Agricultural use Country (km3/yr) (m3/p/yr) (%) (%) (%) 5,409 28 3 3 94 2,782 59.84 16 11 74 2,154 1.64 2 1 98 2,097 66 7 15 79 2,015 56 7 3 90 1,625 11.5 5 4 91 1,558 26.7 4 10 86 1,518 482.2 13 46 41 1,441 8 3 4 93 1,367 1,489 4 20 76 1,344 1.8 3 96 1 1,330 45.08 20 69 11 1,278 0.67 4 3 93 1,243 93.3 7 1 92 1,115 4.8 22 4 74 1,097 3.7 11 2 87 1,064 1.17 8 1 91
Turkmenistan
Turkmenistan gets most of its water from the Amu Darya River. The Qaraqum Canal is a canal system that takes water from the Amu Darya River and distributes the water out over the desert for irrigation of its orchard crops and cotton. Turkmenistan uses the most water per capita in the world because only 55% of the water delivered to the fields actually reaches the crops.
Kazakhstan and Uzbekistan