Seawater 97.5%

Fresh water

2.5%

Ice caps and glaciers

1.97%

Other water

(lakes, rivers, soil

moisture, atmosphere)

0.03%

Groundwater

0.5%

Distribution of Earth’s water

10

WATER: A LIMITED GLOBAL RESOURCE

A

lthough three-fourths of Earth’s surface is covered with

water, substantially less than 1 percent is available for

human use (see graph). Around the world, about 1.1 billion

people live without adequate access to water—many have

fewer than 10 L (about 2.6 gal) of clean water per day. In

contrast, the typical American uses about 340 L (90 gal)

each day.

The U.N. Development Program (UNDP) estimates that

inhabitants of the slums in Lagos, Nigeria, pay 5 to 10 times

as much for water as do those in wealthier neighborhoods

(see photograph, where a woman fills a tub from a communal

tank). In some places, the poor spend as much as 20 percent

of their income on water.

In developed nations, complex systems are in place to

make water available: Utility companies purchase, transport,

clean, and distribute water. The total cost might be large,

but coordination makes the cost per person relatively low

for a reliable water supply. Contrast this with the slums of

Lagos, where there is little money to develop and maintain

infrastructure, so water from pipes is sporadic, and it might

be contaminated. Water might be purchased from a vendor,

but supplies and prices are unpredictable, and the quality of

the water is unknown. Boiling the water to kill off biological

contaminants requires energy, which is also in limited supply.

The UNDP asserts that access to enough safe water—

at least 20 L (5.2 gal) per day—should be considered a

basic human right. The agency has accordingly proposed

strategies to make water available at a low cost, develop

water infrastructure, and hold water providers accountable

for consistency and safety. While enough water exists in the

world for all people, problems of distribution and quality

assurance, increasing global population, and water supply

disruption due to climate change make universal access to

water an issue that will face us for decades to come.

Freshwater

Resources and

Water Pollution

graphingactivity

Interpreting Data

Which of the categories displayed is diminishing due

to rising temperatures associated with global climate

change? How will this impact the other categories?