Facing The Freshwater Crisis
As demand for freshwater soars, planetary supplies are
becoming unpredictable. Existing technologies could
avert a global water crisis, but they must be
implemented soon
becoming unpredictable. Existing technologies could
avert a global water crisis, but they must be
implemented soon
By Peter Rogers
Scientific American Magazine
July 23, 2008
A friend of mine lives in a middle-class neighborhood of
New Delhi, one of the richest cities in India. Although
the area gets a fair amount of rain every year, he wakes
in the morning to the blare of a megaphone announcing
that freshwater will be available only for the next
hour. He rushes to fill the bathtub and other
receptacles to last the day. New Delhi's endemic
shortfalls occur largely because water managers decided
some years back to divert large amounts from upstream
rivers and reservoirs to irrigate crops.
New Delhi, one of the richest cities in India. Although
the area gets a fair amount of rain every year, he wakes
in the morning to the blare of a megaphone announcing
that freshwater will be available only for the next
hour. He rushes to fill the bathtub and other
receptacles to last the day. New Delhi's endemic
shortfalls occur largely because water managers decided
some years back to divert large amounts from upstream
rivers and reservoirs to irrigate crops.
My son, who lives in arid Phoenix, arises to the low,
schussing sounds of sprinklers watering verdant suburban
lawns and golf courses. Although Phoenix sits amid the
Sonoran Desert, he enjoys a virtually unlimited water
supply. Politicians there have allowed irrigation water
to be shifted away from farming operations to cities and
suburbs, while permitting recycled wastewater to be
employed for landscaping and other nonpotable
applications.
schussing sounds of sprinklers watering verdant suburban
lawns and golf courses. Although Phoenix sits amid the
Sonoran Desert, he enjoys a virtually unlimited water
supply. Politicians there have allowed irrigation water
to be shifted away from farming operations to cities and
suburbs, while permitting recycled wastewater to be
employed for landscaping and other nonpotable
applications.
As in New Delhi and Phoenix, policymakers worldwide
wield great power over how water resources are managed.
Wise use of such power will become increasingly
important as the years go by because the world's demand
for freshwater is currently overtaking its ready supply
in many places, and this situation shows no sign of
abating. That the problem is well-known makes it no less
disturbing: today one out of six people, more than a
billion, suffer inadequate access to safe freshwater. By
2025, according to data released by the United Nations,
the freshwater resources of more than half the countries
across the globe will undergo either stress-for example,
when people increasingly demand more water than is
available or safe for use-or outright shortages. By
midcentury as much as three quarters of the earth's
population could face scarcities of freshwater.
wield great power over how water resources are managed.
Wise use of such power will become increasingly
important as the years go by because the world's demand
for freshwater is currently overtaking its ready supply
in many places, and this situation shows no sign of
abating. That the problem is well-known makes it no less
disturbing: today one out of six people, more than a
billion, suffer inadequate access to safe freshwater. By
2025, according to data released by the United Nations,
the freshwater resources of more than half the countries
across the globe will undergo either stress-for example,
when people increasingly demand more water than is
available or safe for use-or outright shortages. By
midcentury as much as three quarters of the earth's
population could face scarcities of freshwater.
Scientists expect water scarcity to become more common
in large part because the world's population is rising
and many people are getting richer (thus expanding
demand) and because global climate change is
exacerbating aridity and reducing supply in many
regions. What is more, many water sources are threatened
by faulty waste disposal, releases of industrial
pollutants, fertilizer runoff and coastal influxes of
saltwater into aquifers as groundwater is depleted.
Because lack of access to water can lead to starvation,
disease, political instability and even armed conflict,
failure to take action can have broad and grave
consequences.
in large part because the world's population is rising
and many people are getting richer (thus expanding
demand) and because global climate change is
exacerbating aridity and reducing supply in many
regions. What is more, many water sources are threatened
by faulty waste disposal, releases of industrial
pollutants, fertilizer runoff and coastal influxes of
saltwater into aquifers as groundwater is depleted.
Because lack of access to water can lead to starvation,
disease, political instability and even armed conflict,
failure to take action can have broad and grave
consequences.
Fortunately, to a great extent, the technologies and
policy tools required to conserve existing freshwater
and to secure more of it are known; I will discuss
several that seem particularly effective. What is needed
now is action. Governments and authorities at every
level have to formulate and execute concrete plans for
implementing the political, economic and technological
measures that can ensure water security now and in the
coming decades.
policy tools required to conserve existing freshwater
and to secure more of it are known; I will discuss
several that seem particularly effective. What is needed
now is action. Governments and authorities at every
level have to formulate and execute concrete plans for
implementing the political, economic and technological
measures that can ensure water security now and in the
coming decades.
Sources of Shortages
Solving the world's water problems requires, as a start,
an understanding of how much freshwater each person
requires, along with knowledge of the factors that
impede supply and increase demand in different parts of
the world. Malin Falkenmark of the Stockholm
International Water Institute and other experts estimate
that, on average, each person on the earth needs a
minimum of 1,000 cubic meters (m3) of water per year-
equivalent to two fifths of the volume of an Olympic-
size swimming pool-for drinking, hygiene and growing
food for sustenance. Whether people get enough depends
greatly on where they live, because the distribution of
global water resources varies widely.
an understanding of how much freshwater each person
requires, along with knowledge of the factors that
impede supply and increase demand in different parts of
the world. Malin Falkenmark of the Stockholm
International Water Institute and other experts estimate
that, on average, each person on the earth needs a
minimum of 1,000 cubic meters (m3) of water per year-
equivalent to two fifths of the volume of an Olympic-
size swimming pool-for drinking, hygiene and growing
food for sustenance. Whether people get enough depends
greatly on where they live, because the distribution of
global water resources varies widely.
Providing adequate water is especially challenging in
drier, underdeveloped and developing nations with large
populations, because demand in those areas is high and
supply is low. Rivers such as the Nile, the Jordan, the
Yangtze and the Ganges are not only overtaxed, they also
now regularly peter out for long periods during the
year. And the levels of the underground aquifers below
New Delhi, Beijing and many other burgeoning urban areas
are falling.
drier, underdeveloped and developing nations with large
populations, because demand in those areas is high and
supply is low. Rivers such as the Nile, the Jordan, the
Yangtze and the Ganges are not only overtaxed, they also
now regularly peter out for long periods during the
year. And the levels of the underground aquifers below
New Delhi, Beijing and many other burgeoning urban areas
are falling.
Shortages of freshwater are meanwhile growing more
common in developed countries as well. Severe droughts
in the U.S., for instance, have recently left many
cities and towns in the northern part of Georgia and
large swaths of the Southwest scrambling for water.
Emblematic of the problem are the man-made lakes Mead
and Powell, both of which are fed by the overstressed
Colorado River. Every year the lakes record their
ongoing decline with successive, chalky high-water marks
left on their tall canyon walls like so many bathtub
rings.
common in developed countries as well. Severe droughts
in the U.S., for instance, have recently left many
cities and towns in the northern part of Georgia and
large swaths of the Southwest scrambling for water.
Emblematic of the problem are the man-made lakes Mead
and Powell, both of which are fed by the overstressed
Colorado River. Every year the lakes record their
ongoing decline with successive, chalky high-water marks
left on their tall canyon walls like so many bathtub
rings.
Golden Rule
Location, of course, does not wholly determine the
availability of water in a given place: the ability to
pay plays a major role. People in the American West have
an old saying: "Water usually runs downhill, but it
always runs uphill to money." In other words, when
supplies are deficient, the powers that be typically
divert them to higher-revenue-generating activities at
the expense of lower-revenue-generating ones. So those
with the money get water, while others do not.
availability of water in a given place: the ability to
pay plays a major role. People in the American West have
an old saying: "Water usually runs downhill, but it
always runs uphill to money." In other words, when
supplies are deficient, the powers that be typically
divert them to higher-revenue-generating activities at
the expense of lower-revenue-generating ones. So those
with the money get water, while others do not.
Such arrangements often leave poor people and nonhuman
consumers of water-the flora and fauna of the adjacent
ecosystems-with insufficient allocations. And even the
best intentions can be distorted by the economic
realities described by that Western aphorism.
consumers of water-the flora and fauna of the adjacent
ecosystems-with insufficient allocations. And even the
best intentions can be distorted by the economic
realities described by that Western aphorism.
A case in point occurred in one of the best-managed
watersheds (or catchments) in the world, the Murray-
Darling River Basin in southeast Australia. Decades ago
the agriculturalists and the government there divided up
the waters among the human users-grape growers, wheat
farmers and sheep ranchers-in a sophisticated way based
on equity and economics. The regional water-planning
agreement allowed the participants to trade water and
market water rights. It even reserved a significant part
of the aqueous resource for the associated ecosystems
and their natural inhabitants, key "users" that are
often ignored even though their health in large measure
underlies the well-being of their entire region. Water
and marsh plants, both macro and micro, for example,
often do much to remove human-derived waste from the
water that passes through the ecosystems in which they
live.
watersheds (or catchments) in the world, the Murray-
Darling River Basin in southeast Australia. Decades ago
the agriculturalists and the government there divided up
the waters among the human users-grape growers, wheat
farmers and sheep ranchers-in a sophisticated way based
on equity and economics. The regional water-planning
agreement allowed the participants to trade water and
market water rights. It even reserved a significant part
of the aqueous resource for the associated ecosystems
and their natural inhabitants, key "users" that are
often ignored even though their health in large measure
underlies the well-being of their entire region. Water
and marsh plants, both macro and micro, for example,
often do much to remove human-derived waste from the
water that passes through the ecosystems in which they
live.
It turns out, however, that the quantities of water that
the planners had set aside to sustain the local
environment were inadequate-an underestimation that
became apparent during periodic droughts-in particular,
the one that has wrought havoc in the area for the last
half a dozen years. The territory surrounding the
Murray-Darling Basin area dried out and then burned away
in tremendous wildfires in recent years.
the planners had set aside to sustain the local
environment were inadequate-an underestimation that
became apparent during periodic droughts-in particular,
the one that has wrought havoc in the area for the last
half a dozen years. The territory surrounding the
Murray-Darling Basin area dried out and then burned away
in tremendous wildfires in recent years.
The economic actors had all taken their share reasonably
enough; they just did not consider the needs of the
natural environment, which suffered greatly when its
inadequate supply was reduced to critical levels by
drought. The members of the Murray-Darling Basin
Commission are now frantically trying to extricate
themselves from the disastrous results of their
misallocation of the total water resource.
enough; they just did not consider the needs of the
natural environment, which suffered greatly when its
inadequate supply was reduced to critical levels by
drought. The members of the Murray-Darling Basin
Commission are now frantically trying to extricate
themselves from the disastrous results of their
misallocation of the total water resource.
Given the difficulties of sensibly apportioning the
water supply within a single nation, imagine the
complexities of doing so for international river basins
such as that of the Jordan River, which borders on
Lebanon, Syria, Israel, the Palestinian areas and
Jordan, all of which have claims to the shared, but
limited, supply in an extremely parched region. The
struggle for freshwater has contributed to civil and
military disputes in the area. Only continuing
negotiations and compromise have kept this tense
situation under control.
water supply within a single nation, imagine the
complexities of doing so for international river basins
such as that of the Jordan River, which borders on
Lebanon, Syria, Israel, the Palestinian areas and
Jordan, all of which have claims to the shared, but
limited, supply in an extremely parched region. The
struggle for freshwater has contributed to civil and
military disputes in the area. Only continuing
negotiations and compromise have kept this tense
situation under control.
Determining Demand
Like supply, demand for water varies from place to
place. Not only does demand rise with population size
and growth rate, it also tends to go up with income
level: richer groups generally consume more water,
especially in urban and industrial areas. The affluent
also insist on services such as wastewater treatment and
intensive farm irrigation. In many cities, and in
particular in the more densely populated territories of
Asia and Africa, water demands are growing rapidly.
place. Not only does demand rise with population size
and growth rate, it also tends to go up with income
level: richer groups generally consume more water,
especially in urban and industrial areas. The affluent
also insist on services such as wastewater treatment and
intensive farm irrigation. In many cities, and in
particular in the more densely populated territories of
Asia and Africa, water demands are growing rapidly.
In addition to income levels, water prices help to set
the extent of demand. For example, in the late 1990s,
when my colleagues and I simulated global water use from
2000 until 2050, we found that worldwide water
requirements would rise from 3,350 cubic kilometers
(km3)-roughly equal to the volume of Lake Huron-to 4,900
km3 if income and prices remained as they were in 1998.
(A cubic kilometer of water is equivalent to the volume
of 400,000 Olympic swimming pools.) But the demand would
grow almost threefold (to 9,250 km3) if the incomes of
the poorest nations were to continue to climb to levels
equivalent to those of middle-income countries today and
if the governments of those nations were to pursue no
special policies to restrict water use. This increased
requirement would greatly intensify the pressure on
water supplies, a result that agrees fairly well with
forecasts made by the International Water Management
Institute (IWMI) when it considered a "business-as-
usual," or "do-nothing-different," scenario in the 2007
study Water for Food, Water for Life.
the extent of demand. For example, in the late 1990s,
when my colleagues and I simulated global water use from
2000 until 2050, we found that worldwide water
requirements would rise from 3,350 cubic kilometers
(km3)-roughly equal to the volume of Lake Huron-to 4,900
km3 if income and prices remained as they were in 1998.
(A cubic kilometer of water is equivalent to the volume
of 400,000 Olympic swimming pools.) But the demand would
grow almost threefold (to 9,250 km3) if the incomes of
the poorest nations were to continue to climb to levels
equivalent to those of middle-income countries today and
if the governments of those nations were to pursue no
special policies to restrict water use. This increased
requirement would greatly intensify the pressure on
water supplies, a result that agrees fairly well with
forecasts made by the International Water Management
Institute (IWMI) when it considered a "business-as-
usual," or "do-nothing-different," scenario in the 2007
study Water for Food, Water for Life.
Ways to Limit Waste
Given the importance of economics and income in water
matters, it is clear that reasonable pricing policies
that promote greater conservation by domestic and
industrial users are worth adopting. In the past the
cost of freshwater in the U.S. and other economic powers
has been too low to encourage users to save water: as
often happens when people exploit a natural resource,
few worry about waste if a commodity is so cheap that it
seems almost free.
matters, it is clear that reasonable pricing policies
that promote greater conservation by domestic and
industrial users are worth adopting. In the past the
cost of freshwater in the U.S. and other economic powers
has been too low to encourage users to save water: as
often happens when people exploit a natural resource,
few worry about waste if a commodity is so cheap that it
seems almost free.
Setting higher prices for water where possible is
therefore near the top of my prescription list. It makes
a lot of sense in developed nations, particularly in
large cities and industrial areas, and more and more in
developing ones as well. Higher water prices can, for
instance, spur the adoption of measures such as the
systematic reuse of used water (so-called gray water)
for nonpotable applications. It can also encourage water
agencies to build recycling and reclamation systems.
therefore near the top of my prescription list. It makes
a lot of sense in developed nations, particularly in
large cities and industrial areas, and more and more in
developing ones as well. Higher water prices can, for
instance, spur the adoption of measures such as the
systematic reuse of used water (so-called gray water)
for nonpotable applications. It can also encourage water
agencies to build recycling and reclamation systems.
Raising prices can in addition convince municipalities
and others to reduce water losses by improving
maintenance of water-delivery systems. One of the major
consequences of pricing water too low is that
insufficient funds are generated for future development
and preventive upkeep. In 2002 the U.S. Government
Accountability Office reported that many domestic water
utilities defer infrastructure maintenance so that they
can remain within their limited operating budgets.
Rather than avoiding major failures by detecting leaks
early on, they usually wait until water mains break
before fixing them.
and others to reduce water losses by improving
maintenance of water-delivery systems. One of the major
consequences of pricing water too low is that
insufficient funds are generated for future development
and preventive upkeep. In 2002 the U.S. Government
Accountability Office reported that many domestic water
utilities defer infrastructure maintenance so that they
can remain within their limited operating budgets.
Rather than avoiding major failures by detecting leaks
early on, they usually wait until water mains break
before fixing them.
The cost of repairing and modernizing the water
infrastructures of the U.S. and Canada to reduce losses
and ensure continued operation will be high, however.
The consulting firm Booz Allen Hamilton has projected
that the two countries will need to spend $3.6 trillion
combined on their water systems over the next 25 years.
infrastructures of the U.S. and Canada to reduce losses
and ensure continued operation will be high, however.
The consulting firm Booz Allen Hamilton has projected
that the two countries will need to spend $3.6 trillion
combined on their water systems over the next 25 years.
When the goal is to save water, another key strategy
should be to focus on the largest consumers. That
approach places irrigated agriculture in the bull's-eye:
compared with any other single activity, conserving
irrigation flows would conserve dramatically more
freshwater. To meet world food requirements in 2050
without any technological improvements to irrigated
agriculture methods, farmers will need a substantial
rise in irrigation water supplies (an increase from the
current 2,700 to 4,000 km3), according to the IWMI
study.
should be to focus on the largest consumers. That
approach places irrigated agriculture in the bull's-eye:
compared with any other single activity, conserving
irrigation flows would conserve dramatically more
freshwater. To meet world food requirements in 2050
without any technological improvements to irrigated
agriculture methods, farmers will need a substantial
rise in irrigation water supplies (an increase from the
current 2,700 to 4,000 km3), according to the IWMI
study.
On the other hand, even a modest 10 percent rise in
irrigation efficiency would free up more water than is
evaporated off by all other users. This goal could be
achieved by stopping up leaks in the water-delivery
infrastructure and by implementing low-loss storage of
water as well as more efficient application of water to
farm crops. An agreement between municipal water
suppliers in southern California and nearby irrigators
in the Imperial Irrigation District illustrates one
creative conservation effort. The municipal group is
paying to line leaky irrigation canals with waterproof
materials, and the water that is saved will go to
municipal needs.
irrigation efficiency would free up more water than is
evaporated off by all other users. This goal could be
achieved by stopping up leaks in the water-delivery
infrastructure and by implementing low-loss storage of
water as well as more efficient application of water to
farm crops. An agreement between municipal water
suppliers in southern California and nearby irrigators
in the Imperial Irrigation District illustrates one
creative conservation effort. The municipal group is
paying to line leaky irrigation canals with waterproof
materials, and the water that is saved will go to
municipal needs.
An additional approach to saving irrigation water
involves channeling water that is eventually intended
for crop fields to underground storage in the nongrowing
season. In most parts of the world, rainfall and snow
accumulation-and runoff to rivers-peak during the
nongrowing seasons of the year, when demand for
irrigation water is lowest. The fundamental task for
managers is therefore to transfer water from the high-
supply season to the high-demand season when farmers
need to irrigate crops.
involves channeling water that is eventually intended
for crop fields to underground storage in the nongrowing
season. In most parts of the world, rainfall and snow
accumulation-and runoff to rivers-peak during the
nongrowing seasons of the year, when demand for
irrigation water is lowest. The fundamental task for
managers is therefore to transfer water from the high-
supply season to the high-demand season when farmers
need to irrigate crops.
The most common solution is to hold surface water behind
dams until the growing season, but the exposure
evaporates much of this supply. Underground storage
would limit evaporation loss. For such storage to be
feasible, engineers would first have to find large
subsurface reservoirs that can be recharged readily by
surface supplies and that can easily return their
contents aboveground when needed for irrigation. Such
"water banks" are currently operating in Arizona,
California and elsewhere.
dams until the growing season, but the exposure
evaporates much of this supply. Underground storage
would limit evaporation loss. For such storage to be
feasible, engineers would first have to find large
subsurface reservoirs that can be recharged readily by
surface supplies and that can easily return their
contents aboveground when needed for irrigation. Such
"water banks" are currently operating in Arizona,
California and elsewhere.
More extensive use of drip-irrigation systems, which
minimize consumption by allowing water to seep in slowly
either from the soil surface or directly into the root
zone, would also do much to stem demand for irrigation
water. Investments in new crop varieties that can
tolerate low water levels and drought, as well as
brackish and even saline water, could also help reduce
requirements for irrigation water.
minimize consumption by allowing water to seep in slowly
either from the soil surface or directly into the root
zone, would also do much to stem demand for irrigation
water. Investments in new crop varieties that can
tolerate low water levels and drought, as well as
brackish and even saline water, could also help reduce
requirements for irrigation water.
Given the rising demand for agricultural products as
populations and incomes grow, it is unlikely that water
managers can significantly lower the quantity of water
now dedicated to irrigated agriculture. But improvements
in irrigation efficiency as well as crop yields can help
hold any increases to reasonable levels.
populations and incomes grow, it is unlikely that water
managers can significantly lower the quantity of water
now dedicated to irrigated agriculture. But improvements
in irrigation efficiency as well as crop yields can help
hold any increases to reasonable levels.
More Steps to Take
Keeping the demand for irrigation water in arid and
semiarid areas down while still meeting the world's
future food requirements can be supported by supplying
"virtual water" to those places. The term relates to the
amount of water expended in producing food or commercial
goods. If such products are exported to a dry region,
then that area will not have to use its own water to
create them. Hence, the items represent a transfer of
water to the recipient locale and supply them with so-
called virtual water.
semiarid areas down while still meeting the world's
future food requirements can be supported by supplying
"virtual water" to those places. The term relates to the
amount of water expended in producing food or commercial
goods. If such products are exported to a dry region,
then that area will not have to use its own water to
create them. Hence, the items represent a transfer of
water to the recipient locale and supply them with so-
called virtual water.
The notion of virtual water may sound initially like a
mere accounting device, but provision of goods-and the
virtual-water content of those goods-is helping many dry
countries avoid using their own water supplies for
growing crops, thus freeing up large quantities for
other applications. The virtual-water concept and
expanded trade have also led to the resolution of many
international disputes caused by water scarcity. Imports
of virtual water in products by Jordan have reduced the
chance of water-based conflict with its neighbor Israel,
for example.
mere accounting device, but provision of goods-and the
virtual-water content of those goods-is helping many dry
countries avoid using their own water supplies for
growing crops, thus freeing up large quantities for
other applications. The virtual-water concept and
expanded trade have also led to the resolution of many
international disputes caused by water scarcity. Imports
of virtual water in products by Jordan have reduced the
chance of water-based conflict with its neighbor Israel,
for example.
The magnitude of annual global trade in virtual water
exceeds 800 billion m3 of water a year; the equivalent
of 10 Nile Rivers. Liberalizing trade of farm products
and reducing tariff restrictions that now deter the flow
of foodstuffs would significantly enhance global
virtual-water flows. Truly free farm trade, for
instance, would double the current annual total delivery
of virtual water to more than 1.7 trillion m3.
exceeds 800 billion m3 of water a year; the equivalent
of 10 Nile Rivers. Liberalizing trade of farm products
and reducing tariff restrictions that now deter the flow
of foodstuffs would significantly enhance global
virtual-water flows. Truly free farm trade, for
instance, would double the current annual total delivery
of virtual water to more than 1.7 trillion m3.
Whatever benefits the world may accrue from virtual-
water transfers, the populations of growing cities need
real, flowing water to drink, as well as for hygiene and
sanitation. The ever expanding demand for urban, water-
based sanitation services can be reduced by adopting
dry, or low-water-use, devices such as dry composting
toilets with urine separation systems. These
technologies divert urine for reuse in agriculture and
convert the remaining waste on-site into an organic
compost that can enrich soil. Operating basically like
garden compost heaps, these units employ aerobic
microbes to break down human waste into a nontoxic,
nutrient-rich substance. Farmers can exploit the
resulting composted organic matter as crop fertilizer.
These techniques can be used safely, even in fairly
dense urban settings, as exemplified by installations at
the Gebers Housing Project in a suburb of Stockholm and
many other pilot projects.
water transfers, the populations of growing cities need
real, flowing water to drink, as well as for hygiene and
sanitation. The ever expanding demand for urban, water-
based sanitation services can be reduced by adopting
dry, or low-water-use, devices such as dry composting
toilets with urine separation systems. These
technologies divert urine for reuse in agriculture and
convert the remaining waste on-site into an organic
compost that can enrich soil. Operating basically like
garden compost heaps, these units employ aerobic
microbes to break down human waste into a nontoxic,
nutrient-rich substance. Farmers can exploit the
resulting composted organic matter as crop fertilizer.
These techniques can be used safely, even in fairly
dense urban settings, as exemplified by installations at
the Gebers Housing Project in a suburb of Stockholm and
many other pilot projects.
Essentially, civil engineers can employ this technology
to decouple water supplies from sanitation systems, a
move that could save significant amounts of freshwater
if it were more widely employed. Moreover, recycled
waste could cut the use of fertilizer derived from
fossil fuels.
to decouple water supplies from sanitation systems, a
move that could save significant amounts of freshwater
if it were more widely employed. Moreover, recycled
waste could cut the use of fertilizer derived from
fossil fuels.
Beyond constraining demand for freshwater, the opposite
approach, increasing its supply, will be a critical
component of the solution to water shortages. Some 3
percent of all the water on the earth is fresh; all the
rest is salty. But desalination tools are poised to
exploit that huge source of salty water. A recent,
substantial reduction in the costs for the most energy-
efficient desalination technology-membrane reverse-
osmosis systems-means that many coastal cities can now
secure new sources of potable water.
approach, increasing its supply, will be a critical
component of the solution to water shortages. Some 3
percent of all the water on the earth is fresh; all the
rest is salty. But desalination tools are poised to
exploit that huge source of salty water. A recent,
substantial reduction in the costs for the most energy-
efficient desalination technology-membrane reverse-
osmosis systems-means that many coastal cities can now
secure new sources of potable water.
During reverse osmosis, salty water flows into the first
of two chambers that are separated by a semipermeable
(water-passing) membrane. The second chamber contains
freshwater. Then a substantial amount of pressure is
applied to the chamber with the salt solution in it.
Over time the pressure forces the water molecules
through the membrane to the freshwater side.
of two chambers that are separated by a semipermeable
(water-passing) membrane. The second chamber contains
freshwater. Then a substantial amount of pressure is
applied to the chamber with the salt solution in it.
Over time the pressure forces the water molecules
through the membrane to the freshwater side.
Engineers have achieved cost savings by implementing a
variety of upgrades, including better membranes that
require less pressure, and therefore energy, to filter
water and system modularization, which makes
construction easier. Large-scale desalination plants
using the new, more economical technology have been
built in Singapore and Tampa Bay, Fla.
variety of upgrades, including better membranes that
require less pressure, and therefore energy, to filter
water and system modularization, which makes
construction easier. Large-scale desalination plants
using the new, more economical technology have been
built in Singapore and Tampa Bay, Fla.
Scientists are now working on reverse-osmosis filters
composed of carbon nanotubes that offer better
separation efficiencies and the potential of lowering
desalination costs by an additional 30 percent. This
technology, which has been demonstrated in prototypes,
is steadily approaching commercial use. Despite the
improvements in energy efficiency, however, the
applicability of reverse osmosis is to some degree
limited by the fact that the technology is still energy-
intensive, so the availability of affordable power is
important to significantly expanding its application.
composed of carbon nanotubes that offer better
separation efficiencies and the potential of lowering
desalination costs by an additional 30 percent. This
technology, which has been demonstrated in prototypes,
is steadily approaching commercial use. Despite the
improvements in energy efficiency, however, the
applicability of reverse osmosis is to some degree
limited by the fact that the technology is still energy-
intensive, so the availability of affordable power is
important to significantly expanding its application.
A Return on Investment
Not surprisingly, staving off future water shortages
means spending money-a lot of it. Analysts at Booz Allen
Hamilton have estimated that to provide water needed for
all uses through 2030, the world will need to invest as
much as $1 trillion a year on applying existing
technologies for conserving water, maintaining and
replacing infrastructure, and constructing sanitation
systems. This is a daunting figure to be sure, but
perhaps not so huge when put in perspective. The
required sum turns out to be about 1.5 percent of
today's annual global gross domestic product, or about
$120 per capita, a seemingly achievable expenditure.
means spending money-a lot of it. Analysts at Booz Allen
Hamilton have estimated that to provide water needed for
all uses through 2030, the world will need to invest as
much as $1 trillion a year on applying existing
technologies for conserving water, maintaining and
replacing infrastructure, and constructing sanitation
systems. This is a daunting figure to be sure, but
perhaps not so huge when put in perspective. The
required sum turns out to be about 1.5 percent of
today's annual global gross domestic product, or about
$120 per capita, a seemingly achievable expenditure.
Unfortunately, investment in water facilities as a
percentage of gross domestic product has dropped by half
in most countries since the late 1990s. If a crisis
arises in the coming decades, it will not be for lack of
know-how; it will come from a lack of foresight and from
an unwillingness to spend the needed money.
percentage of gross domestic product has dropped by half
in most countries since the late 1990s. If a crisis
arises in the coming decades, it will not be for lack of
know-how; it will come from a lack of foresight and from
an unwillingness to spend the needed money.
There is, however, at least one cause for optimism: the
most populous countries with the largest water
infrastructure needs-India and China-are precisely those
that are experiencing rapid economic growth. The part of
the globe that is most likely to continue suffering from
inadequate water access-Africa and its one billion
inhabitants-spends the least on water infrastructure and
cannot afford to spend much; it is crucial, therefore,
that wealthier nations provide more funds to assist the
effort.
most populous countries with the largest water
infrastructure needs-India and China-are precisely those
that are experiencing rapid economic growth. The part of
the globe that is most likely to continue suffering from
inadequate water access-Africa and its one billion
inhabitants-spends the least on water infrastructure and
cannot afford to spend much; it is crucial, therefore,
that wealthier nations provide more funds to assist the
effort.
The international community can reduce the chances of a
global water crisis if it puts its collective mind to
the challenge. We do not have to invent new
technologies; we must simply accelerate the adoption of
existing techniques to conserve and enhance the water
supply. Solving the water problem will not be easy, but
we can succeed if we start right away and stick to it.
Otherwise, much of the world will go thirsty.
global water crisis if it puts its collective mind to
the challenge. We do not have to invent new
technologies; we must simply accelerate the adoption of
existing techniques to conserve and enhance the water
supply. Solving the water problem will not be easy, but
we can succeed if we start right away and stick to it.
Otherwise, much of the world will go thirsty.
_____________________________________________
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