Population Growth, Water Shortages
The world's population, at nearly 6 billion, is growing by about 80 million people
each year. This number implies an increased demand for freshwater of about 64
billion cubic meters a year—an amount equivalent to the entire annual flow rate of the
Rhine River. While population growth rates have slowed somewhat, the absolute
number of people added to the population each year—the relevant figure when
considering the availability of and need for freshwater—remains near historic highs.
For example, because nearly 2 billion people have been added to the planet since
1970, per capita availability of water is one-third lower now than it was then.
China and India, the world's first and second most populous countries, provide
examples of how even modest population growth rates translate into large absolute
numbers when the population base is large. In China the population growth rate is
about 1% per year, estimated in 1998. Nevertheless, because China's population is
over 1.2 billion people, even a low population growth rate means 12 million
additional people each year. India's population growth rate, which is substantially
higher than China's, at about 1.9% per year, means about 18 million people added
each year to India's current population of about 970 million.
In the two regions of the world that already face the most serious absolute or seasonal
shortages of water—Africa and the Near East—population growth rates remain
among the highest in the world. In sub-Saharan Africa population is growing by an
average 2.6% a year; in the Near East and North Africa, by 2.2%. These population
growth rates have ominous implications for per capita water supply in the countries of
these regions. Water stress and scarcity. As their populations grow, more and more
countries are facing water shortages. A country is said to experience water stress
when annual water supplies drop below 1,700 cubic meters per person. At levels
between 1,700 and 1,000 cubic meters per person, periodic or limited water shortages
can be expected. When annual water supplies drop below 1,000 cubic meters per
person, the country faces water scarcity. Once a country experiences water scarcity, it
can expect chronic shortages of freshwater that threaten food production, hinder
economic development, and damage ecosystems.
Malin Falkenmark developed the concepts of water stress and water scarcity based on
an index of per capita freshwater needs. She estimated a minimum need of 100 liters
per day per person for household use and from 5 to 20 times as much for agricultural
and industrial uses. These concepts have been widely accepted and used by
hydrologists, the World Bank, and other organizations. For example, Population
Action International (PAI) has relied on them to make projections of per capita water
availability and to forecast water shortages in 2025 and 2050.
Calculations of water stress and water scarcity are based on estimates of a country's
renewable freshwater supplies and do not include water withdrawn from fossil
groundwater. Fossil groundwater is essentially a nonrenewable resource: It takes tens
of thousands of years for these deep aquifers to replenish themselves. A country may
temporarily avoid the effects of water stress by mining its nonrenewable water
supplies, but this practice is not sustainable, particularly if the population continues to
grow rapidly and per capita demand for freshwater increases.
As of 1995, 31 countries, with a combined population of over 458 million, faced
either water stress or water scarcity. This represents an addition of only 3 countries
since 1990, when 28 countries, with a combined population of 335 million faced
chronic water stress or water scarcity. The number of people estimated to live in
water-scarce and water-stressed countries rose by nearly 125 million during these five
years, however, largely reflecting population growth in water-short countries.