Withdrawing Liquid Assets
How Demographic Trends Affect the Freshwater Supply
ENERGY AND ENVIRONMENT
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E
Many Human Activities Tap the
Freshwater Supply
Human use of fresh water is commonly divided into
three sectors: agricultural, industrial, and domestic.
The figure shows the proportions of water demand
by sector for six continents and the world.
In agriculture, which accounts for nearly 70
percent of all freshwater usage worldwide, farmers
use water to irrigate crops and maintain livestock.
In industry, which accounts for about 20 percent
of water withdrawals worldwide, manufacturing
and other processes consume water for functions
such as cooling and cleaning. And in everyday
life, people draw on water for many domestic
uses, including drinking, cooking, cleaning, and
landscaping, and these activities account for the
remaining 10 percent. Among the continents,
the relative quantities of water withdrawals differ
notably across the sectors. However, the agricultural sector dominates water withdrawals, and its
influence generally decreases with higher levels of
industrialization. Only in South America and Africa
does the domestic sector withdraw more water
than does the industrial sector, reflecting relatively
Water availability has become a pressing
concern in recent years due to unprecedented growth in the earth’s human population.
Demographic factors, including population
size, distribution, and composition, influence
the demand for fresh water in agriculture,
industry, and domestic life. To avoid a worldwide water crisis, water management policies must address the impact of these factors
on both supply and demand and establish
reforms to enable people to use the existing
freshwater supply more efficiently.
low levels of industrialization. Because of the many
ways in which people use fresh water, the world’s
changing demographics have a strong influence on
the future of the Earth’s freshwater supply.
Estimated Sectoral Water Withdrawals by
Region, 1995 (Percent of Annual Total)
100
80
60
40
20
0
Domestic
Industry
W
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EDUCATION
A
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CIVIL JUSTICE
Abstract
Th
e
CHILD POLICY
ven though Earth has 1.4 billion cubic
kilometers of water, only 200,000 cubic
kilometers of it (0.014 percent) is fresh
water accessible for human use. Water availability has become a pressing concern in the past
few decades because of unprecedented growth in
the human population—the demand for fresh water
continues to grow while the supply remains finite.
Demographic factors, such as population size, distribution, and composition, influence the demand
for fresh water both directly and indirectly. A report
recently published by Population Matters, a RAND
Corporation project, explains that knowing the
effects of each of these factors is critical to understanding the future of water resources and designing
effective, sustainable water-management policies.
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THE ARTS
Sectoral withdrawals as
% of annual withdrawals
RAND RESEARCH AREAS
Agriculture
SOURCE: United Nations and World Meteorological
Organization, Comprehensive Assessment of
Freshwater Resources of the World, New York:
World Meteorological Organization, 1997.
Changing Demographics Can Strain Water
Resources
Population size, number of households, urbanization, and economic
development all influence the amount of water withdrawn and the
quality of the water available.
Population Size and Number of Households
In the 20th century, the world’s population grew from 1.65 billion
to six billion, and now in the 21st century, the population continues to grow. Although the relationship is not linear, larger populations generally require more water than do smaller ones. The number of households worldwide has also increased, and at a faster rate
than population has grown. Lower fertility rates, higher divorce
rates, aging populations, and a decline in multigenerational family
units all contribute to the increase in the number of households.
The increased number of households affects freshwater resources
in two ways. First, members of smaller households consume more
water and create more waste on a per-capita basis because they lack
the economies of scale available to members of larger households.
Their smaller size also makes investments in technical water-saving
measures less cost effective; for example, a water-saving toilet costs
the same amount whether it serves a household of one or eight.
Second, the transition toward smaller household size requires more
housing units, which cover more land. When the land is paved,
polluted and unfiltered water flows directly to bodies of water and
diminishes the quality and quantity of the freshwater supply.
Migration and Urbanization
Migration affects water resources through the changes it creates in
the landscape. People may migrate from one location to another
due to deforestation, desertification, drought, or lack of arable
land. A shortage of water or suitable farmland may drive people to
migrate to cities, where urbanization puts further pressure on the
available water resources.
Urbanization has increased greatly worldwide in the last half
century, and urban populations are expected to match rural ones
in size by 2007. This increase in urbanization has a number of consequences for water resources. First, the density of population in
cities concentrates high demand on the local water resources, which
depletes the local water supply and disrupts the local ecosystems.
With further growth, cities tap into new sources farther away and
extend the negative effects on the environment. Second, urban
areas often create more waste than the surrounding environment
can absorb. The increased waste and changes in land use result
eventually in groundwater contamination, which further reduces
the supply of fresh water. Third, urban areas are more likely to use
waterborne sanitation systems, which flush waste into a sewage system in which the water must be treated. These sanitation systems
alone increase the demand for fresh water by about 40 liters per
capita per day.
Sanitation and access to clean water are critical health concerns
because of water’s key role in fighting disease. In the developing
world, rapidly expanding cities and rural areas with inadequate
water and sanitation infrastructures face greater health risks due to
the lack of clean water for drinking and washing.
Economic Development
A country’s level of economic development also influences its freshwater use. Developed countries tend to use water more efficiently
than do developing countries, especially in the industrial sector.
However, because of greater economic activity, they also use more
water per capita to run industry, grow food, produce electricity, and
process waste. Furthermore, populations in industrialized countries use more water to support individual and societal lifestyles,
and they demand more water-intensive products and services (e.g.,
water-borne sanitation systems, energy products, and manufactured
goods, which may require large amounts of water to produce).
Water Management Can Mitigate the Effects of
Changing Demographics
Localized and regional water problems will continue to plague
areas with unfavorable physical, social, economic, and cultural conditions. However, a worldwide water crisis can be averted through
improved water management practices that take into account the
influence of demographics on local and global resources, as well as
the importance of mitigating factors such as economic development
and the sectoral distribution of water. New water-management policies must aim to reduce the impact of demographic factors, such as
population growth, urbanization, and the increase in the number
of households. Some of the tools available for managers are those
that help to reduce demand and augment supply. On the demand
side, they include market-based incentives, nonmarket instruments
(e.g., laws and regulations), and direct interventions. Tools on the
supply side include spatial reallocation, temporal reallocation, water
harvesting, reclamation, and desalination. Equally important is a
revamping of the governance of many water systems. Some areas
may require comprehensive reforms to enable people to use existing
supplies of water efficiently rather than continuing to deplete the
freshwater supply.
This research brief describes work done for the Population Matters project of RAND Labor and Population documented in Liquid Assets: How Demographic Changes and Water
Management Policies Affect Freshwater Resources, by Jill Boberg, MG-358-CF (available at http://www.rand.org/publications/MG/MG358/), 2005, 108 pp., $18.00, ISBN: 0-83303807-9. MG-358 is also available from RAND Distribution Services (phone: 310.451.7002 or email: order@rand.org). The RAND Corporation is a nonprofit research organization
providing objective analysis and effective solutions that address the challenges facing the public and private sectors around the world. RAND’s publications do not necessarily reflect
the opinions of its research clients and sponsors. R® is a registered trademark.
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THE ARTS
CHILD POLICY
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CIVIL JUSTICE
EDUCATION
ENERGY AND ENVIRONMENT
HEALTH AND HEALTH CARE
INTERNATIONAL AFFAIRS
NATIONAL SECURITY
This product is part of the RAND Corporation
research brief series. RAND research briefs present
policy-oriented summaries of individual published, peerreviewed documents or of a body of published work.
POPULATION AND AGING
PUBLIC SAFETY
SCIENCE AND TECHNOLOGY
SUBSTANCE ABUSE
TERRORISM AND
HOMELAND SECURITY
TRANSPORTATION AND
INFRASTRUCTURE
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organization providing objective analysis and effective
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