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5 Sustaining Our Freshwater Resources

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Learning Outcomes

After reading this chapter, you should be able to

• Describe how New York City worked with nature to improve its water supply.
• Illustrate the water cycle and how the planet’s water is distributed.
• Define different types of water use.
• Analyze the methods used to meet global water demand.
• Describe the potential for global conflict over water.
• Describe different types of water pollution and ways to manage that pollution.
• Differentiate between the hard path and soft path approaches to water management.
• Discuss the role of forests in water management.

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146

Section 5.1 Case Study: New York City’s Water Supply

When viewed from space, Earth is a watery planet, with oceans covering over 70% of the
planet’s surface and glaciers, ice caps, lakes, rivers, and streams covering another 10%. Yet
water shortages and access to clean, safe drinking water are a serious problem in virtually
every region of the world. The abundance of ocean water is too salty for human use, and much
of the freshwater is either polluted or inaccessible.

Given its importance and critical role in all human life, it is remarkable how poorly managed
water is as a resource. We regularly use rivers, streams, and the oceans as a dumping ground
for our wastes and allow contaminants like spilled oil and agricultural chemicals to pollute
critical groundwater supplies. We dam rivers and use massive amounts of energy to pump
water hundreds of miles to irrigate golf courses and suburban lawns in the middle of deserts.
And we pay little attention to how the management—or mismanagement—of natural capital
resources like forests, wetlands, and other open spaces impacts water quality in surrounding
regions.

This chapter will examine issues of freshwater management and consider the challenges of
both water quantity and water quality. The next chapter will examine issues and challenges
associated with our oceans.

We will first discuss issues of water quantity, which involve ensuring that there are adequate
supplies and that mismanagement of water does not result in flooding. Only a tiny fraction
of water on the planet is accessible and suitable for human consumption, making wise water
management a critical priority. We’ll also see that just as with other critical resources like
food and energy, water use varies greatly in different regions of the world. We will then con-
sider issues of water quality, which involve ensuring that water is safe to use. Lastly, we will
look at ideas and approaches for water conservation and sustainable water management,
including efforts both to increase the availability of water on the supply side and to reduce
usage on the demand side.

5.1 Case Study: New York City’s Water Supply

New York City has long prided itself on the quality of its municipal drinking water, with some
residents and city boosters going so far as to call it the “champagne of tap water.” Over the
years the city has garnered awards for the quality of its water relative to other major cities
in the United States, and chefs and food experts have debated whether the city’s water might
have something to do with the quality of its pizza and bagels. A Southern California–based
pizza business even goes so far as to spend $10,000 a year to have New York City tap water
trucked across the country to use in making dough for its New York–style pizza.

The story of why New York City’s water quality is so good and how the city addressed contam-
ination can help us begin to understand the issues discussed in this chapter and the impor-
tance of sustaining freshwater resources.

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147

Section 5.1 Case Study: New York City’s Water Supply

Building a Water Supply System
As far back as the 1830s, city leaders in New York knew that, in order for the city to grow and
thrive, they needed to do something about their water supply situation. At the time, the city
drew its water from a patchwork of ponds, springs, and underground wells, but overuse and
poor waste management were affecting both the quantity and the quality of the city’s water
supply. Massive fires burned through wood-framed buildings because water pressure was
too low to fill fire hoses. Overpumping of wells led freshwater levels to fall below sea level,
allowing the nearby ocean to seep in and contaminate groundwater supplies. The raw sew-
age and animal waste being dumped in the streets ran off and contaminated ponds and small
reservoirs.

After a cholera epidemic (due in large part to poor water quality) killed thousands in 1832
and the Great Fire of New York burned 17 city blocks in 1835, city leaders embarked on a
massive water development project that would change the course of New York City history.
A dam was built on the Croton River north of the city, and a 65-kilometer (40-mile) covered
aqueduct was built to carry water from there to the middle of Manhattan, where Central Park
is located today. When the new water supply system opened in 1842, it carried 340 million
liters (90 million gallons) of clean water every day to the thirsty city.

Sixty years later, the system was expanded
on as city officials sought to prevent water
shortages and inadequate supply while
New York City grew and expanded. Water
development projects were undertaken fur-
ther north and west of the city in the Catskill
Mountain region. An entire series of dams,
reservoirs, aqueducts, and tunnels were
constructed in the early 1900s, and by 1915
the Catskill Aqueduct was in operation.

Today New York City’s water supply system
is still based almost entirely on the projects
from the 1800s and early 1900s. Each day
over 4.5 billion liters (1.2 billion gallons)
of water are delivered to New York City’s
9 million residents, with 10% of this water
coming from the Croton portion of the system and 90% originating from the Catskill portion.
The Catskill watershed region, over 160 kilometers (100 miles) away from the city, draws
water from 19 reservoirs and 3 lakes spread out over a 500,000-hectare (2,000-square-mile)
area. A watershed is an area of land where sources of water (streams, creeks) flow together
to a single destination. These lakes and reservoirs are connected to the city by 10,000 kilome-
ters (over 6,200 miles) of pipes, tunnels, and aqueducts. Because of differences in elevation,
almost the entire system moves water through gravity, with a drop of water taking anywhere
from 3 months to 1 year to travel from an upstate lake or reservoir to a customer in the city. As
the water approaches the city, it’s treated with chlorine to kill germs and pathogens, as well
as fluoride for dental health and a couple of other chemicals to prevent corrosion of pipes.

Elizabeth Petrozello/iStock /Getty Images Plus
The Ashokan Reservoir in the Catskill
Mountains is one of several to provide New
York City with its water supply.

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148

Section 5.1 Case Study: New York City’s Water Supply

Unlike most major urban water systems, New York City’s drinking water is not filtered. In fact,
New York has the largest unfiltered drinking water system in the United States. New York’s
water supply reservoirs were built in upstate areas that were covered in forests and that
also had vast areas of intact wetlands. These forests and wetlands act as natural sponges and
filters, absorbing rainfall and snowmelt and purifying the water in the process. Many other
cities that draw their drinking water from nearby lakes and rivers need to have expensive fil-
tration systems to remove sediment and other particles and contaminants before distributing
water to residents.

Learn More: New York City’s Water Supply

To get a sense of how vast the Catskill watershed region is, visit the following link:

https://www.dec.ny.gov/docs/water_pdf/nycsystem.pdf

Expanding Ecosystem Management
By the 1990s, however, things began to change for the worse in terms of New York City’s
drinking water. Increased development, road building, suburban sprawl, and other activities
in the Catskill region were having a negative impact on water quality in surrounding reser-
voirs and lakes. U.S. Environmental Protection Agency (EPA) inspectors warned the city that
it might have to build a $10 billion water filtration plant to address the issue.

Instead, New York City decided to take a different approach. The 1997 Watershed Memoran-
dum of Agreement (MOA) was negotiated between New York City, New York State, the EPA,
environmental groups, and municipalities and townships in the Catskills region. The MOA
committed New York City to spend just under $2 billion on a range of initiatives intended to
improve water quality in the Catskill reservoirs. These initiatives included purchasing and
protecting lands surrounding reservoirs and lakes, as well as paying nearby landowners who
agreed not to develop their lands commercially. In addition, the city helped upstate communi-
ties improve wastewater treatment plants, assisted dairy farmers with manure management,
and worked with road departments to ensure that runoff from roads and highways was not
entering reservoirs. Lastly, the city provided funding for upstate home owners to upgrade sep-
tic systems and for forest landowners to improve forest management practices. Collectively,
these approaches are known as ecosystem management because they focus on maintaining
water quality at the source rather than cleaning the water as it reaches its destination. Over
the past 20 years, the ecosystem management initiatives undertaken as part of the MOA have
proved effective enough that the EPA has granted New York City a series of “filtration avoid-
ance determinations” that allow the city to operate its water system without a filtration plant.

The ecosystem management approach has been supplemented with high-tech features,
including a network of hundreds of robotic buoys deployed across reservoirs to continually
test and monitor water quality. These robotic water quality monitors test over 1.9 million
water samples each year. In addition, the city has recently put in place the world’s largest
ultraviolet water disinfection facility. Water passes through containers mounted with ultra-
violet lights that kill any microorganisms that might contaminate the water and make con-
sumers sick.

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149

Section 5.2 Freshwater Systems

While New York City water officials must always be vigilant in ensuring the quality of the
city’s water, the success of the MOA initiatives points to the importance of “source manage-
ment” as an approach to meeting our water needs. Rather than spend $10 billion building
a water filtration plant to treat polluted water at the back end of the system, New York City
spent one fifth of that amount to ensure that its drinking water was not polluted at the source
in the first place. Essentially, New York City has been investing in the natural capital resources
of forests and wetlands in the Catskills region and letting this natural infrastructure provide
the ecosystem service of keeping the city’s water clean.

5.2 Freshwater Systems

Water is perhaps the most critical resource to human well-being and survival. Our bodies are
made up of as much as 60% water, and while healthy individuals can survive weeks without
food, they would last only a few days without water. We also rely on water to grow food,
produce energy, and manufacture just about everything imaginable. In addition, we depend
on and benefit from a range of ecosystem functions and services provided by water, includ-
ing transportation, recreational activities, and wildlife habitat. We regularly rely on rivers,
streams, and oceans to dilute and purify our waste products, although this use frequently
conflicts with the other ecosystem functions and services that water provides. Despite all the
ways we depend on water, we seldom give much thought to where it comes from and how it
gets to us.

Water Distribution
It’s been said that we live on a “blue planet,” since water covers nearly three fourths of the
Earth’s surface. However, when we account for where water is located and what condition it
is in, we realize that water is not only a critical natural capital resource but also a scarce one.
How can it be that such an abundant resource can also be scarce at the same time?

Imagine the world’s water as 1 million individual 1-gallon containers. (In reality, there are
370 million trillion gallons.) For starters, about 970,000 (97%) of those containers would
be filled with salty ocean water unsuitable for human consumption. It was this reality that
inspired the line from The Rime of the Ancient Mariner, “water water everywhere, nor any drop
to drink” (Coleridge, 1919/1990, lines 121–122). Another 26,100 gallons (2.61%) would be
filled with ice and snow—nearly all of it from ice caps and glaciers in the Arctic and Antarctic
regions, far from major human populations. Roughly 3,600 gallons (0.36%) would be filled
with groundwater, with much of this (but not all, as we will learn) consisting of salt water also
unsuitable for human consumption.

Out of the 1 million gallons we started with, only 300 gallons remain. Some of those 300 gal-
lons consist of water vapor in the atmosphere, water found in saline or salty lakes, or water
in the soil, leaving just about 180 gallons (0.018%) of fresh surface water—water on the
surface of the Earth, found in rivers, wetlands, lakes, and reservoirs. Because this fresh sur-
face water is the primary source of water for most people on the planet, we can see just how
scarce and precious this resource actually is. (See Figure 5.1.)

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150

Section 5.2 Freshwater Systems

Thankfully, nature has a way of constantly recycling, replenishing, and purifying water sources.
In fact, unlike other resources (such as fossil fuels) that are permanently “consumed,” global
water supply is more or less fixed. This is because of the global hydrologic cycle. The hydro-
logic cycle, or water cycle, describes the movement of water between the planet’s surface,
atmosphere, soil, oceans, and living organisms. If we think again of our 1 million gallon con-
tainers, the water cycle is constantly moving water among the different containers, although
human activities are increasingly interfering with this process and further complicating effec-
tive water management.

Water Cycle
The global water cycle is driven primarily by solar energy. Heat from the sun causes water to
evaporate from surface waters and land surfaces and enter the atmosphere as water vapor.
For example, it’s estimated that solar energy evaporates roughly 425,000 cubic kilometers
(km3) of ocean water each year. To put that in perspective, just 1 cubic kilometer of water is

Figure 5.1: Water distribution

Only 0.6% of the world’s freshwater—0.018% of all water on Earth—is readily available as surface water
for human use.

Source: Data adapted from “Where Is Earth’s Water?” by US Geological Survey, n.d. (https://www.usgs.gov/media/images/distribution
-water-and-above-earth).

Earth’s water

Freshwater
3%

Other
0.4%

Fresh surface
water (liquid)

0.6%

Ice caps
and glaciers

87%

Groundwater
12%

Saline
(oceans)

97%

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151

Section 5.2 Freshwater Systems

equivalent to a tank of water that is 1,000 meters (3,280 feet) tall, wide, and long, or 1 tril-
lion liters (265 billion gallons). The amount of energy it takes to move this much water from
the ocean to the atmosphere is massive. Roughly one third of all the solar energy striking the
Earth each day is used to drive evaporation.

In addition to evaporation, plants draw massive amounts of water from the soil and release
some of that water to the atmosphere as water vapor through a process known as transpira-
tion. Evaporation and transpiration are together known as evapotranspiration. As water
vapor from evapotranspiration rises into the atmosphere, it cools and condenses to form
clouds (condensation) before falling back to Earth as rain and snow (precipitation). Evapo-
ration, transpiration, condensation, and precipitation form the basis of the water cycle (see
Figure 5.2).

Figure 5.2: The water cycle

The basis of the hydrologic cycle is condensation, precipitation, and evapotranspiration. Once water
reaches the ground, it either runs off into nearby bodies of water or infiltrates the surface, where it
reaches the water table and underground aquifers.

Source: Based on “Ground Water and Surface Water a Single Resource,” by US Geological Survey, 2013 (https://pubs.usgs.gov/circ
/circ1139/).

Groundwater flow

Surface runoff
Snow
runoff

Well

Groundwa
ter flow

Lake

Groundwater
discharge

Evaporation

Water table

Condensation

Precipitation

Groundwater
discharge

Con
densation

Transpiration

E
v

a
p

o
transpiration

Pr

ec
ip

it
at

io
n

The processes of evaporation and condensation purify water naturally because only water
molecules are pulled into the atmosphere, leaving any salts, contaminants, or pollutants
behind. This is basically the same as making distilled water by boiling water and condensing
the vapor. Roughly 90% of the ocean water evaporated each year falls back as precipitation
over the oceans, where it mixes again with salt water. However, about 10% of that moisture
falls over land surfaces as freshwater precipitation.

An even larger amount of freshwater precipitation is provided by evapotranspiration from
plants and forests. In tropical forests as much as 80% of all precipitation comes from the
direct recycling of evapotranspiration from plants. This feedback loop—more trees leading to
more transpiration leading to more precipitation leading to more trees—is a key reason why
forest management is so tightly linked with water management.

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152

Section 5.2 Freshwater Systems

Overall, of the 110,000 km3 of precipitation that falls over land surfaces each year, it’s esti-
mated that roughly one third comes from moisture drawn from ocean waters and two thirds
from moisture from evapotranspiration from plants. This 110,000 km3 of precipitation ends
up doing one of three things. First, about two thirds of that water evaporates back into the
atmosphere from land surfaces or through plant transpiration. The other one third either
flows over land and enters rivers, streams, and lakes (surface water) or gradually percolates
through soil and rock to enter underground aquifers (groundwater). It’s this relatively small
amount of water, roughly 37,500 km3 per year, that replenishes the tiny sliver of fresh surface
water illustrated in Figure 5.1 and represents the total renewable supply of fresh surface
water on the planet. As with most other resources, this freshwater supply is unevenly dis-
tributed around the world. Atmospheric circulation patterns, topography, and proximity to
water sources and forests are all factors that influence the amount of precipitation in a given
location.

Human Impact on the Water Cycle
Human activities can also affect precipitation patterns and what happens to that precipitation
after it falls to Earth. Under normal conditions, as precipitation reaches the ground, some of
it is pulled below the surface by gravity through a process known as infiltration. This water
eventually reaches the water table, a depth below ground where soil and rock are completely
saturated with water. The saturated area immediately below the water table is known as an
aquifer, an area of permeable rock and sediment from which water can be extracted.

Many communities, private home owners, factories, and farmers use pumps to pull ground-
water from aquifers to the surface. As long as rates of infiltration are the same or greater than
rates of extraction, the water level in the aquifer will be maintained. However, this is often not
the case, and overpumping is resulting in aquifer depletion in many locations, such as with
the Ogallala Aquifer in the U.S. Midwest (recall Chapter 4). As New York City discovered in
the 1830s, overpumping of water from aquifers near the ocean can also cause the problem
of saltwater intrusion as lower freshwater levels in the aquifer allow adjacent salt water
to enter and contaminate that supply. Saltwater intrusion is a worsening problem in coastal
regions around the world today.

Land use on the surface also affects how
quickly aquifers can recharge. Developed
areas like cities and suburbs have replaced
grassland and forest soils with a lot of imper-
meable surface area. Most roads, driveways,
parking lots, and roofs of buildings do not
allow rain and melting snow to infiltrate
into the ground and instead increase run-
off. This increased runoff can result in more
floods as too much water moves too fast
across the surface and is not absorbed into
the ground. Recent research demonstrates
how too much impermeable surface area
greatly worsened the impacts of Hurricane
Harvey in Houston in 2017 (Zhang, Villarini,

Cameron Whitman/iStock/Thinkstock
Heavily developed and paved areas create
a problem for our water supply, since rain
and snow cannot easily penetrate back into
the Earth.

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153

Section 5.3 Global Water Use and Demand

Vecchi, & Smith, 2018). More and more cities, municipalities, developers, and home owners
are beginning to consider ways to cut down on water runoff and increase rates of infiltration
in order to increase and improve groundwater supplies as well as prevent flooding.

The water cycle makes available the freshwater that all human life relies on, constantly recy-
cling and replenishing this scarce resource. Unfortunately, human activities such as over-
pumping of groundwater and paving of surface areas are negatively impacting both the quan-
tity and quality of our water supply. This is happening at the same time that global water
use and demand is increasing with population growth. The next section takes a closer look
at global water use and how that demand can be met, given the finite supply of freshwater
available to us.

5.3 Global Water Use and Demand

Recall that an estimated 110,000 km3 of precipitation falls over land surfaces each year and
that 37,500 km3 of this enters surface waters or percolates into underground aquifers. This
37,500 km3 represents the theoretical supply of renewable freshwater on the planet each
year. If all this water were available to us, it would be more than enough to meet human needs.
However, a few factors complicate this picture.

First, where this precipitation falls does not
always align with where humans reside.
For example, large amounts of precipita-
tion fall to the ground and flow to the sea
in sparsely populated regions of the Ama-
zon basin in South America or in remote
areas of central Africa. Second, when this
precipitation falls can make water manage-
ment challenging even in very wet places.
For example, in tropical regions of Asia that
experience heavy rainfall, as much as 80%
to 90% of annual precipitation can fall dur-
ing just a few months of the monsoon, with
relatively dry conditions prevailing for the
other months of the year.

As a result, and despite adequate supplies of water on average globally, we face water short-
ages and scarcity in many regions. Over 2 billion people lack access to adequate and safe water
supplies, and over 4 billion lack access to proper sanitation (World Water Assessment Pro-
gramme, 2019). As a result, at least 2 million preventable deaths occur each year from water-
related diseases that mostly claim the lives of young children (WHO, n.d.b). In some cases,
problems arise from an absolute scarcity of water, whereas in others there is inadequate infra-
structure to meet a population’s water requirements. This section will consider those issues of
water quantity: its use and demand and how human water needs are being met.

Antoninapotapenko/iStock /Getty Images Plus
Tropical regions such as Asia can get 80% to
90% of their total annual rainfall in as little as
3 months due to natural weather conditions.

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154

Section 5.3 Global Water Use and Demand

Let us return to the 37,500 km3 that represents the theoretical supply of renewable fresh-
water each year. As much as half runs off the surface and to the sea in uncaptured floodwa-
ter. Humans build dams and other barriers to try to capture some of that runoff, but as we
will discuss, that brings its own problems and challenges. Another 20% of the 37,500 km3
of global freshwater supply is in regions that are not readily accessible. That leaves us with
roughly 12,500 km3 of what is known as reliable surface runoff, and it is this amount that
is actually available for human use and consumption. So how do we make use of this reliable
surface runoff ? What are the environmental impacts of that use? And why do so many people
around the world still face water scarcity and shortages?

How Water Is Used
Because we use and rely on water in so many different ways, we can measure water consump-
tion differently as well. For starters, it’s estimated that humans already appropriate over half
of the 12,500 km3 of reliable surface runoff each year, leaving less than half for all other spe-
cies and organisms on the planet. We can first divide that human use or appropriation into
two broad categories: instream uses and extractive uses.

Instream uses of water refers to the ways in which we use water without actually extracting
it from its physical location. For example, water-based recreational activities like boating and
waterskiing are common on many lakes and rivers in countries like the United States. While
these activities do not involve a direct consumption of water, they may compete with or pre-
vent the use of that water for other purposes.

Extractive uses of water refers to situations in which water is physically removed from its
source location. In some cases this involves actual consumption, while others involve using
and then returning the water to its source. For example, when water is extracted from a river
or aquifer and used to irrigate a farm field, most of that water will evaporate to the atmo-
sphere. This represents a consumptive use of water. In contrast, hydroelectric power plants
divert large amounts of water from rivers and lakes to generate electricity (see Section 7.12),
but that water flows back to the same river or lake. This represents a nonconsumptive use
of water. The Apply Your Knowledge feature examines the environmental impact of noncon-
sumptive use.

Apply Your Knowledge: What Is the Environmental Impact of
Nonconsumptive Water Use?

You can probably imagine the environmental impacts of chemical pollution and water
consumption, but what about nonconsumptive water use?

To explore this question, consider the Brazilian Nuclear Power Plant (BNPP) in southeastern
Brazil. The facility withdraws water from Ilha Grande Bay to cool equipment. Afterward, that
water is returned to the bay. Aside from a small amount of water that is lost to evaporation,
no materials are added or removed during the process.

(continued)

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155

Section 5.3 Global Water Use and Demand

Apply Your Knowledge: What Is the Environmental Impact of
Nonconsumptive Water Use? (continued)

In a 2012 study, researchers investigated the environmental impacts of BNPP on Ilha
Grande Bay (Teixeira, Neves, & Araújo, 2012). Researchers collected measurements of
fish biodiversity and abundance near the power plant (within 200 meters) and in similar
environments farther away (more than 1,500 meters). They then compared the two locations
to highlight any differences. Some of these results are shown in Figure 5.3.

Figure 5.3: Impact of BNPP on biodiversity and fish abundance

Species biodiversity (a) and fish abundance (b) in Ilha Grande Bay. “Close” locations are less
than 200 meters and “far” locations more than 1,500 meters from the BNPP facility.

Source: Data from “Thermal Impact of a Nuclear Power Plant in a Coastal Area in Southeastern Brazil: Effects of Heating and
Physical Structure on Benthic Cover and Fish Communities,” by T. P. Teixeira, L. M. Neves, and F. G. Araujo, 2012, Hydrobiologia,
684.

Close

(a)

(b)

12

11

10

9

8

7

6

5

4

3

2

1

0

Far

N
u

m
b

e
r

o
f

s
p

e
c
ie

s

Close

150

100

50

0

Far

N
u

m
b

e
r

o
f

fi
s
h

(continued)

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156

Section 5.3 Global Water Use and Demand

Apply Your Knowledge: What Is the Environmental Impact of
Nonconsumptive Water Use? (continued)

The first chart suggests that there is significantly less biodiversity (fewer species of fish)
close to the power plant than there is farther away. In the second chart, the difference
between the two measurements is small compared with the uncertainties of the two
measurements. There appears to be a similar number of fish in both locations.

Take a moment to consider this data along with what you know about water use in this
location. Can you explain how the power plant might be impacting fish in the surrounding
ecosystem?

The power plant is affecting ecosystems by altering environmental conditions. According
to the temperature data in the Ilha Grande Bay study, the water near BNPP is more than 4
degrees Celsius warmer than its surroundings (see Figure 5.4).

When the power plant cools off its equipment, the process warms the water that is extracted.
This raises the temperature of bay locations with close proximity to BNPP. While many fish
species can survive the cooler temperatures of the greater bay, relatively few have been able
to thrive close to the power plant. With less competition, the species that can tolerate the
warmer water are also able to achieve larger populations than they do elsewhere. The result
is an environment that still has life but that is severely diminished in terms of biodiversity.

Figure 5.4: Impact of BNPP on water temperature

Temperatures at Ilha Grande Bay study locations.

Source: Data from “Thermal Impact of a Nuclear Power Plant in a Coastal Area in Southeastern Brazil: Effects of Heating
and Physical Structure on Benthic Cover and Fish Communities,” by T. P. Teixeira, L. M. Neves, and F. G. Araujo, 2012,
Hydrobiologia, 684.

Close

30

28

26

24

Far

T
e
m

p
e
ra

tu
re

(
°C

)

(continued)

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157

Section 5.3 Global Water Use and Demand

Who Uses Water (and How Much)
Globally, agriculture is the largest user of water, accounting for about 70% of all extractive
water uses. However, this global average masks wide variations in water consumption by sec-
tor and in the overall amounts of water consumed. For example, in Africa and Asia agriculture
accounts for over 80% of all water use, whereas in more industrialized countries of Europe,
only 20% goes to agriculture while 60% goes to industry (Food and Agriculture Organiza-
tion of the United Nations, 2016). Figure 5.5 shows a breakdown of average water use in the
United States. But even within the United States, there can be significant variations in these
figures. Most water use in the more industrialized and populated regions of the Northeast is
for power plants, industry, and residential uses. In drier regions of the West and Southwest,
over 80% of water use is for agriculture (Dieter et al., 2018).

Per capita levels of water consumption also vary widely among different regions of the world
(see Table 5.1). This is partly a result of water supply and the infrastructure needed to deliver
that water to people when and where they need it. It’s also a function of factors like standard
of living, how efficiently water is used in that country, the kinds of economic activities under-
taken there, and the food choices people make. Water consumption generally increases with
standard of living, and countries that produce highly water-intensive products like cotton
and beef tend to have higher rates of per capita water use. This is one of the reasons why the
United States and Australia, both big producers and consumers of beef, have some of the high-
est rates of per capita water consumption in the world.

Apply Your Knowledge: What Is the Environmental Impact of
Nonconsumptive Water Use? (continued)

When industries like BNPP impact the environment by adding heat, we call it thermal
pollution. Thermal pollution affects both freshwater and marine ecosystems like the one in
Ilha Grande Bay. According to a recent study, the Mississippi River absorbs more heat from
nonconsumptive water use than any other river in the world. Meanwhile, the Rhine River in
Europe experiences the most significant temperature increases from thermal pollution of
any major river. Coal and nuclear power plants serve as the pollution sources in both cases
(Raptis, Van Vliet, & Pfister, 2016).

Thermal pollution is an example of a 21st-century environmental problem. Like many of
our most pressing issues, it is the result of complex human and environmental systems that
interact in sometimes unexpected ways. It demonstrates that we need to do more than just
reduce material flows if we want a sustainable future. We also need to understand systems
holistically and consider all the environmental factors that allow life to thrive.

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Section 5.3 Global Water Use and Demand

Figure 5.5: Water use in the United States

These pie charts show average water use across the United States, but the breakdown can vary
significantly by region.

Source: Adapted from “Summary of Estimated Water Use in the United States in 2015,” by US Geological Survey, 2018 (https://pubs.usgs
.gov/fs/2018/3035/fs20183035.pdf ); adapted from “Residential End Uses of Water, Version 2,” by US Environmental Protection Agency
and Water Research Foundation, 2016 (https://www.waterrf.org/research/projects/residential-end-uses-water-version-2).

Water use in the United States,
by category (2015)

Household water use in the United States,
by activity (2016)

Agriculture
37.4%

Electric
power
41.4%

Aquaculture
2.3%

Industry and mining
5.8%

Residential
and

commercial
13.1%

Toilet
24%

Shower
20%Faucet

19%

Other
8%

Leak
12%Clothes

washer
17%

Table 5.1: Annual per capita water use around the world (1996–2005)

Low (<1,000 m3) Medium (1,000–2,000 m3) High (>2,000 m3)

Bangladesh 769 South Africa 1,255 Israel 2,303

Rwanda 821 Japan 1,379 Australia 2,315

Nicaragua 912 Thailand 1,407 Canada 2,333

Malawi 936 Germany 1,426 Spain 2,461

Guatemala 983 France 1,786 United States 2,842

Note. 1 m3 = 264 gallons.

Source: Data from “The Water Footprint of Humanity, by A. Y. Hoekstra and M. M. Mekonnen, 2012, Proceedings of the National
Academy of Sciences, 109 (https://waterfootprint.org/en/resources/waterstat/national-water-footprint-statistics).

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159

Section 5.3 Global Water Use and Demand

The example of beef illustrates an important concept known as virtual water, or embodied
water. We may not think about it, but just about every item we use or consume required water
to produce. In terms of food items, for example, it takes roughly 15,415 liters (4,072 gallons)
of water to produce one kilogram of beef, and 1,608 liters (425 gallons) of water to produce
enough wheat for a kilogram of bread (see Figure 5.6). But water is also used to produce
nonfood items as well. For example, it takes roughly 5,400 liters (1,427 gallons) of water to
produce one pair of jeans. For comparison, we use about 75 to 100 liters (20 to 26 gallons) of
water for an average 10-minute shower.

Figure 5.6: Virtual water

This graph illustrates the liters of water needed to produce a kilogram of each of these food items. The
amount of water required to produce the food we eat is not always obvious.

Source: Data from “Product Gallery,” by Water Footprint Network, n.d. (https://waterfootprint.org/en/resources/interactive-tools/product
-gallery/).

287

560

790

822

1,020

1,220

1,420

1,608

3,178

3,300

4,325

5,988

15,415

17,196

18,900

Potatoes

Oranges

Bananas

Apples

Milk

Corn

Beer

Bread

Cheese

Eggs

Chicken

Pork

Beef

Chocolate

Coffee

Liters of water

20,00010,000 15,0005,0000

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160

Section 5.3 Global Water Use and Demand

The virtual water concept helps illustrate how consumption decisions made in one location
can impact water supply and management issues in another. In recent years California has
been experiencing severe droughts and water shortages, and yet this state alone produces
over a third of America’s vegetables and two thirds of its fruits and nuts. It’s estimated that
the average American consumes over 1,100 liters (290 gallons) of California water every
week by eating food products grown there (Buchanan, Keller, & Park, 2015). The virtual water
concept also makes even clearer the problem of food loss and waste discussed in Chapter 4.
Every time we waste food, we are also wasting all the water (and energy; see Chapter 7) used
in the production of that food.

Challenges of Meeting Water Demand
Many regions of the world are already experiencing, or will soon experience, serious chal-
lenges in meeting their water needs. Water scarcity refers to a situation in which there is
a physical, volume-based lack of water. It’s estimated that close to 700 million people in 43
countries around the world currently experience water scarcity and that this number could
more than double in the next decade (United Nations Department of Economic and Social
Affairs [UNDESA], n.d.b). Water stress, in contrast, is a broader term that includes physi-
cal scarcity as well as issues of water quality and the accessibility or affordability of clean
water supplies. Over 1 billion people are currently experiencing water stress, and this figure
could grow as high as 4 billion in the decades ahead unless more effective and efficient water
management practices are implemented (UNDESA, n.d.b). Later sections in this chapter will
highlight ways we can address water scarcity and stress, as well as challenges related to water
quality. Before that, however, let’s have a look at some areas where meeting water demand is
proving difficult.

Water Rationing in South Africa
One of the most high-profile and recent examples of water scarcity is playing out in the city
of Cape Town, South Africa. Cape Town is a modern, bustling metropolis and a major tourist
destination located at the southern tip of the African continent. It has a population (4 million)
and climate similar to Los Angeles in Southern California.

After 3 years of severe drought and poor water management decisions, the city began to warn
residents and businesses in late 2017 of “Day Zero,” the day when municipal water would

Learn More: Your Water Footprint

There are a number of sources that allow you to explore and calculate your “water footprint”
in different ways.

• https://waterfootprint.org/en
• https://www.watercalculator.org
• https://water.usgs.gov/edu/activity-percapita.html

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161

Section 5.3 Global Water Use and Demand

be completely cut off and water would be
available only through centralized distribu-
tion points. Cape Town was set to become
the first modern major city in the world to
run dry.

Severe restrictions on residential and agri-
cultural water use and a return to more
normal rainfall patterns in the latter half of
2018 helped Cape Town postpone Day Zero,
but the water situation there is still precari-
ous. Residents are still limited to using 50
liters (13 gallons) of water per day, farms
outside the city have had their irrigation
supplies cut off, and long lines can still be
found at natural springs and grocery stores
when supplies of bottled water are deliv-

ered. Cape Town offers a cautionary tale of how even major cities can be at risk of water scar-
city, especially as global climate change alters precipitation patterns and weather.

Dams in China and the United States
One way to try to alleviate water scarcity and stress is through the construction of dams and
water diversion projects. Dams are built across rivers to capture and store surface runoff in
reservoirs. Dams can be utilized to control runoff to prevent floods, generate hydroelectric-
ity, and supply water for agricultural, industrial, and residential uses. There are over 800,000
dams around the world, including close to 50,000 “large dams” that are 15 meters (50 feet)
or higher. Combined, these dams capture and store close to 15% of global surface runoff for
human uses. In the United States that figure is closer to 50%.

While dams can provide many benefits in terms of water supply and management, energy
production, and recreation, they also have a number of problems associated with them. First,
when rivers are dammed, they create reservoirs behind the dam that can displace entire com-
munities. For example, China’s massive Three Gorges Dam (the largest in the world) displaced
1.2 million people and flooded 13 cities, 140 towns, and 1,350 villages. Second, dams can have
dramatic impacts on native fish and wildlife species as well as alter important ecosystem
functions and services that rivers provide. For example, a series of large dams on the Colorado
River have fundamentally altered that ecosystem and reduced the flow of water from that
river to the ocean to virtually a trickle.

Competing Water Use Along the Colorado
The Colorado River also offers an example of a regional water system threatened by misman-
agement, competing demands between users, and global climate change. The Colorado River
originates on the western slopes of the Rocky Mountains in Colorado. From there it flows
2,400 kilometers (1,500 miles) to the Gulf of California in Mexico. Along the way, the Colorado
River passes through mountain regions, deserts, and the Grand Canyon.

Bram Janssen/Associated Press
Residents of Cape Town, South Africa, waiting
in line for water. Water resources in Cape Town
are at a premium, and restrictions are in place
in response to severe water shortages.

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162

Section 5.3 Global Water Use and Demand

Almost 100 years ago, water managers in
western states began a systematic process
of building dams on the Colorado River
and using massive water diversion systems
to divide the river’s water between urban
areas and agriculture. Today nearly 40 mil-
lion people in cities such as Las Vegas, Phoe-
nix, Los Angeles, and San Diego depend on
water from the Colorado River, while over
70% of the water withdrawn is used to irri-
gate 1.4 million hectares (3.5 million acres)
of cropland that produces 15% of U.S. agri-
cultural products.

Since at least 2000, however, warning signs
have been flashing for Colorado River water
managers and others in the region. Water
levels in Lake Mead and Lake Powell (fed by the Colorado) have dropped dramatically, reveal-
ing water lines like “bathtub rings” that show where the water level used to be. Decreasing
winter snowfall totals in the Rocky Mountains, tied to global climate change, lead to reduced
runoff and water supply in the summer months. Water shortages in the region are projected
to get even worse with climate change, and water managers are already struggling to balance
competing demands for water from urban and residential users versus agricultural users.
Meanwhile, regional energy managers are making contingency plans for possible electricity
shortages caused by declining hydroelectric production from the region’s dams.

Water Diversion and the Aral Sea
An even more dramatic example of water misuse and mismanagement comes from central
Asia. The Aral Sea, located on the border between Kazakhstan and Uzbekistan, was once the
world’s fourth largest lake and roughly the size of the country of Ireland. Up until the 1960s
the Aral Sea supported hundreds of lakeside communities, provided an estimated 60,000 jobs
in the fishing industry, and provided important wildlife habitat and ecosystem services for
the region (Bennett, 2008).

At the time, the region was part of the Soviet Union, and Soviet engineers and planners made
the decision to divert water from two major rivers, the Syr Darya and the Amu Darya, that
fed freshwater to the Aral Sea. The water was to be used for irrigation for cotton and wheat
production. Dozens of large dams, almost 100 reservoirs, and over 30,000 kilometers (20,000
miles) of canals were constructed.

Gradually, the Aral Sea began to shrink in size, and by 2000 it split into a small northern por-
tion and a larger southern portion. A few years after that, the southern portion split again
into an eastern and western half. And in just the past few years, the southeastern portion has
dried up completely. Overall, the Aral Sea has lost over 90% of the water it once contained.
The former lakeside is littered with the rusted hulks of old fishing boats, and strong winds
whip up dust storms that blow over former lakeside communities and sicken whatever resi-
dents still remain.

Filippobnf/iStock /Getty Images Plus
Damming of the Colorado River has drastically
reduced the water level of Lake Mead. Here the
former water level is indicated by the bathtub-
like rings around the edges.

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163

Section 5.4 Water and Global Politics

Meeting the challenge of water demand is made all the more difficult because water is a
“transboundary” resource that moves across national borders and boundaries. This fact, com-
bined with rising populations and the threat of water shortages, has made water resources a
potential source of conflict between nations. This issue, and the idea of adequate water as a
fundamental human right, will be the focus of the next section.

5.4 Water and Global Politics

In 2010 the United Nations (UN) passed a resolution that explicitly recognized “safe and clean
drinking water and sanitation” (UN, n.d.c, p. 1) as fundamental human rights. The resolution
recognizes that drinking water supplies should be sufficient, safe, physically accessible, and
affordable (UNDESA, n.d.a). While the UN resolution does not specify what countries have to
do to meet this human right, it does call attention to the seriousness of the problem and estab-
lish a clear baseline of human water requirements at 50 to 100 liters (13 to 26 gallons) per
day. The UN cites research by WHO estimating that 24,000 children die every day from diar-
rhea and other preventable diseases caused by polluted water. This research also estimates
that millions of women and girls in developing countries walk an average of 6 kilometers
(almost 4 miles) every day to collect water for their families. This daily chore takes a physical
toll and prevents young girls from completing schooling that might improve their lives.

The UN resolution comes at a time when two global challenges could be exacerbating issues
of water availability and sanitation. As described in Chapter 3, global population is approach-
ing 8 billion and is projected to hit 10 billion later this century. Increased population means
increased water demand for direct and indirect (virtual water) uses, such as for agriculture.
In addition, global climate change (discussed in more detail in Chapter 8) is complicating

University of Maryland Global Land Cover Facility and NASA, Earth Observatory
The Aral Sea has lost over 90% of the water it once contained and has split into
several smaller seas. Before water diversion projects began in the 1960s, the Aral
Sea was the fourth-largest lake in the world. By 1989 (left), the northern and
southern part had begun to split. Between 2000 (middle) and 2009 (right), the
southern part dried up almost completely. Water levels have remained essentially
the same since 2009.

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164

Section 5.4 Water and Global Politics

the water supply picture. Climate change is lead-
ing to changing weather and precipitation patterns,
including more intense rains (and runoff ) in short
periods and prolonged droughts in others. Cli-
mate change is shifting where and when precipita-
tion falls as well, making it difficult to predict and
manage water supplies for a growing population.
Finally, climate change and warming are leading
to increased evaporation from surface water sup-
plies and faster melting and retreat of major gla-
ciers around the world. At least 200 million people
depend almost exclusively on melting water from
glaciers for their water supply, and in some of these
places the glaciers are melting so fast that they are
at risk of disappearing.

This combination of population growth and global
climate change has led some experts to predict that
major wars of the 21st century are more likely to be
fought over water than any other resource, includ-
ing energy. While the link between water and con-
flict has a long history, current conditions appear to
be increasing the likelihood of future “water wars.”
There are 261 major river systems around the
world that cross national borders. When upstream
populations dam, divert, pollute, or somehow interfere with the quantity or quality of water
flowing downstream, there is the potential for conflict.

Currently, some of the most contentious regions where a water war is likely to break out
include the Nile River basin in Africa, the Euphrates–Tigris basin in the Middle East, and the
Mekong River basin in Southeast Asia. The Nile River flows through parts of 11 countries.
Dam construction in upstream countries like Ethiopia could result in tension and conflict
with downstream nations like Sudan and Egypt. In the Euphrates–Tigris basin, major water
diversion projects for irrigation in Turkey have affected river flow to Syria and Iraq. In the
Mekong River basin, upstream dam construction, particularly in China, has altered down-
stream water flows and ecosystems. China has used its political influence and power to ignore
complaints from other affected countries.

Even in the United States, there are numerous examples of legal conflict between states over
water rights and access. The most well known of these disputes involve management of and
access to Colorado River water in the arid Southwest. But even in the relatively wetter region
of the American Southeast, a 30-year conflict over water is playing out. The “tri-state water
wars” pit Alabama and Florida against Georgia over management of water from the Alabama-
Coosa-Tallapoosa (ACT) and Apalachicola-Chattahoochee-Flint (ACF) river basins. Upstream
Atlanta depends heavily on these river basins for meeting its municipal water needs, and
as the city’s population has grown, so has its use of these waters. In 1990 Alabama sued to
prevent Atlanta from taking additional water from lakes fed by the ACT and ACF river basins.
Eventually, Florida joined in the conflict, and in 2018 portions of the tri-state dispute reached
as high as the U.S. Supreme Court before being remanded to the lower courts.

lubilub/iStock/Thinkstock
The UN has deemed drinking water a
fundamental right. In many parts of
the world, women and girls must walk
miles each day to collect water for
basic needs.

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165

Section 5.5 Water Quality

Meeting the world’s demand for adequate water supplies needs to involve considerations of
supply, management, and the necessity of that demand. Further complicating the picture are
the issues of global climate change, discussed in Chapter 8, and water pollution, the focus of
the next section. One approach to better meeting regional water demand is through privatiza-
tion of water systems (see the Learn More feature box).

Learn More: Water Privatization

A somewhat controversial approach to managing municipal water systems is known as
water privatization. Typically, city and municipal water systems around the world have been
managed by government agencies or public utilities, whose primary goal was to deliver
adequate water to residents at the lowest cost possible. However, in some cities these
agencies and utilities were poorly managed and experienced high rates of water leaks and
wastage. As a result, water privatization was proposed as a solution. Privatization involves
selling water systems to private companies to manage on a for-profit basis.

Supporters of privatization argue that private sector companies are more efficient, are better
able to manage large-scale water supply systems, and have the financial capital to invest
in upgrades and other improvements to these systems. Critics argue that privatization is
a violation of the principle of water as a human right, since it makes water a commodity
that can be denied to individuals who lack the financial resources to pay for it. The reality
probably lies somewhere in between, with a lot depending on how privatization is handled
and what restrictions and requirements are placed on the company taking over a water
system.

To learn more about water privatization and arguments for and against this approach, visit:

• https://blogs.ei.columbia.edu/2010/09/02/what-is-the-benefit-of-privatizing-
water

• https://pacinst.org/wp-content/uploads/2002/02/new_economy_of_water3.pdf
• https://www.foodandwaterwatch.org/insight/water-privatization-facts-and-

figures
• https://www.citizen.org/wp-content/uploads/top10-reasonstoopposewaterpriva

tization.pdf
• https://www.forbes.com/sites/adammillsap/2016/10/05/privatizing-water-

facilities-can-help-cash-strapped-municipalities/#318792184b5c

5.5 Water Quality

Up until this point most of our discussion has focused on issues of water supply and availabil-
ity, or water quantity. This section will take a closer look at the threats to water quality from
various forms of pollution and what’s being done to address it.

For as long as humans have lived in groups, they have diluted biological wastes by discarding
them in nearby streams, rivers, and other bodies of water. As human populations grew, and
as economic activity became increasingly industrialized and concentrated, the volume and
character of that waste also changed. However, the solution to pollution remained dilution,
and as a result, our waterways became more and more polluted over time.

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166

Section 5.5 Water Quality

In the United States this approach began to result in some dramatic and frightening examples
of water pollution by the 1950s and 1960s. For example, pollution of Lake Erie was so bad by
the 1960s that the lake was declared virtually dead and lifeless. In June 1969 the Cuyahoga
River in Cleveland, Ohio, caught fire due to buildup of oil and debris on the river’s surface.

News stories and headlines featuring these and other water pollution disasters helped result
in water-quality regulations that addressed some of the most glaring problems. However,
threats to water quality and new forms of water pollution continue to be a challenge. The EPA
(2016) recently completed a national assessment of rivers and streams. It reported that over
half of river and stream miles in the United States are severely polluted, impaired, or in poor
condition, meaning that those waterways did not meet federal water-quality standards.

Classifying Pollutants
The most basic breakdown of water pollution is between what are known as point sources
and nonpoint sources of pollutants (see Figure 5.7). Point sources are fixed and stationary
sources of water pollutants, such as a drainage pipe from a factory or discharge from a sew-
age treatment plant. Nonpoint sources are diffuse sources of pollution that are difficult to
pinpoint. For example, cow manure running off of a farm field, lawn chemicals washed off of
suburban lawns, and sediment washed into nearby streams and rivers from a construction
site are all cases of nonpoint source pollution.

Figure 5.7: Nonpoint vs. point sources of pollutants

Nonpoint sources of pollutants are diffuse and more difficult to manage, whereas point sources are fixed
and stationary.

Nonpoint sources Point sources

Car oil, trash, animal waste,
chemicals used on farms

and lawns can end up
in storm drains and

into bodies of water.

Factories, sewage treatment
plants, large-scale animal

feeding operations, and others
dispose of waste directly into

bodies of water.

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167

Section 5.5 Water Quality

Regardless of whether pollutants are from a point source or nonpoint source, they can be
further classified into different types. The most common are listed in Table 5.2. All of these
pollutants impair water quality in some fashion.

Table 5.2: Common types and sources of water pollutants

Type of pollutant Common sources

Pathogens Animal waste

Nutrients Fertilizers, CAFOs, sewage treatment plants

Sediment and soil Farms, construction sites

Oil Parking lots, tanker and pipeline spills

Plastics Litter, landfills

Heavy metals Industry

Toxic substances Pesticides, industry

Heat (thermal pollution) Power plants

Another type of water pollutant that is causing increased concern is chemical compounds in
items that we consume or use in our homes every day. For example, triclosan is an antibacte-
rial and antifungal agent used in soaps, toothpastes, deodorants, and lotions. This chemical is
washed down the drain and eventually enters rivers and streams, where it can be toxic to fish
and other aquatic life. Likewise, ecologists have measured detectable levels of birth control
hormones, antibiotics, caffeine, and other substances in hundreds of streams and rivers in
the United States. Because these chemicals are not removed from wastewater in most waste-
water treatment plants, they are excreted from our bodies and washed down drains before
entering rivers, streams, and other waterways. Once there they can have serious detrimental
impacts on fish and other forms of aquatic wildlife.

Managing Nonpoint Source Pollution
Managing nonpoint sources of water pollution is much more challenging than addressing
point source pollution because nonpoint pollution of a waterway can originate from hun-
dreds or even thousands of locations. After the high-profile water pollution disasters of the
1950s and 1960s, federal legislation was passed that targeted major point source polluters
like factories and sewage treatment plants. But water pollution from nonpoint sources like
agriculture (soil erosion, fertilizer runoff, manure runoff ) and urban or suburban develop-
ment (lawn chemicals, parking lots and streets, sediment from construction projects) has
continued to worsen since then. In the example of New York City at the start of this chapter,
nonpoint sources were causing problems with the city’s drinking water supply.

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168

Section 5.5 Water Quality

One of the most serious types of nonpoint pollution from agriculture is runoff of animal
wastes and fertilizers, which can cause algal blooms, eutrophication, and aquatic dead zones.
To prevent runoff, water-quality experts encourage farmers to practice some of the sustain-
able agricultural techniques described in Chapter 4, including contour farming and low-till or
no-till agriculture. It also helps if farmers leave space for riparian buffers. A riparian buffer
is a vegetated strip of land alongside a stream or river. The trees, shrubs, grasses, and other
plants in a riparian buffer help trap soil, sediment, and other pollutants before they can enter
a waterway. In New York City part of the funding provided to upstate farmers was to help
establish and maintain riparian buffers in agricultural areas.

In urban and suburban areas, runoff of fertilizer from lawns, golf courses, and parks can also
contribute to eutrophication and dead zones. Large amounts of water and melting snow run-
ning off of roofs, streets, parking lots, and driveways can cause both water-quantity problems,
such as flooding, and water-quality problems as runoff picks up potential pollutants like road
salt and oil spilled from cars and trucks. Here too, establishing riparian buffers around urban
areas can help cut down on pollution entering waterways and slow the rate at which runoff
enters streams and rivers, reducing flood risks downstream. Protecting existing wetlands and
even establishing “constructed wetlands” that contain plants that can slow urban/suburban
runoff and absorb excess nutrients can also help minimize nonpoint source pollution. Other
approaches are outlined in Table 5.3. All of these approaches fall under the umbrella of water-
shed management, and they play an important part in the approach used to protect New York
City’s water supply. They also have in common the idea that it is better to try to prevent pollu-
tion from entering waterways in the first place than try to clean it up after it’s already there.

Table 5.3: Approaches for minimizing urban and suburban runoff

Approach Description

Riparian buffers Vegetated strips of land alongside streams and rivers

Green roofs A roof that is covered in plants and can absorb rainwater

Rain gardens A garden in a depressed area that collects rainwater

Permeable pavement A porous urban surface that allows rainwater to seep into the ground
instead of running off

Wetlands Swamps and marshes that contain plants that absorb nutrients and
improve water quality

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169

Section 5.5 Water Quality

One of the most challenging forms of water pollution involves contamination of groundwa-
ter supplies. Unlike surface water pollution, groundwater pollution is hidden from view and
potentially “out of sight and out of mind.” Groundwater pollution is also much more difficult
to clean up than surface water pollution. Whereas streams and rivers naturally flush them-
selves clear through running water, contaminants that enter groundwater get trapped there
and can take years or decades to break down or dissipate. Major sources of groundwater
pollution include leaks from industrial storage tanks, septic systems, and underground gaso-
line tanks, as well as seepage of agricultural chemicals like pesticides and fertilizers. In addi-
tion, hydraulic fracturing, or fracking, of oil and gas wells is increasingly being implicated in
the contamination of municipal and residential groundwater supplies in some regions of the
United States (see Learn More: Fracking and Water Quality).

Learn More: Fracking and Water Quality

Over the past couple of decades, there has been rapid development and growth in the use of
an oil- and gas-drilling technique known as hydraulic fracturing, or fracking. Fracking allows
oil and gas companies to remove these fuels from oil shale rock formations that previously
were not considered viable for exploitation (see Section 7.4). In fracking, liquids mixed
with sand (collectively known as fracking fluid) are pumped into oil shale deposits under
extremely high pressures. This fractures and cracks the shale formations while the sand
keeps the cracks open just enough to allow the oil and gas to begin to flow to the surface.

In theory, fracking should not have much of an impact on groundwater, since shale deposits
are located far below the surface and well below the water table and aquifers that homes
and municipalities draw drinking water from. However, the fracking process creates a
number of opportunities for groundwater contamination, and there is growing evidence that
this process has been impacting water quality in regions of the country where fracking is
widespread (including Pennsylvania, Wyoming, and Colorado). For example, leaks of fracking
fluid from the drill hole have been documented, as well as leaks of contaminated water that
“flows back” (known as flowback water) to the surface. Likewise, poor management and
handling of fracking fluid and flowback water at the well site can lead to spills and seepage of
these fluids into groundwater deposits.

The oil and gas industry has adamantly denied a link between fracking activities and changes
in water quality, while a major 2016 EPA report found that fracking could impact water
quality under “certain conditions” if the process is not managed properly. Nevertheless, as
fracking has grown in importance throughout the United States, and as well operations have
aged, the number of reports of water-quality impact from fracking activities has also grown.

More information on the links between fracking and water quality can be found at these
sites:

• https://www.epa.gov/hfstudy
• https://www.bbc.com/news/uk-37578189
• https://e360.yale.edu/features/as_fracking_booms_growing_concerns_about

_wastewater
• http://worldwater.org/wp-content/uploads/2013/07/ww8-ch4-fracking.pdf

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Section 5.5 Water Quality

There is also growing concern over groundwater contamination by a class of chemicals
known as per- and polyfluorinated alkyl substances, or PFAS. PFAS are used in a number of
products, including firefighting foam and waterproofing materials, and exposure to them has
been linked to various forms of cancer, pregnancy complications and low birth weights, liver
damage, thyroid disease, asthma, and reduced fertility. PFAS pollution is especially problem-
atic on dozens of military bases around the country due to heavy use there in firefighting
operations. The Union of Concerned Scientists (2018) reports that of 131 military sites tested
for PFAS in their groundwater used for drinking, only 1 was within the safe limit. Forty-three
sites had drinking water with PFAS levels that were 1 to 100 times over the safe limit, and 87
sites had PFAS levels more than 100 times greater than the safe limit.

Managing Point Source Pollution
Overall, serious water pollution problems
from point sources like factories have
become much less of a problem in countries
like the United States due to laws and regu-
lations. The U.S. Clean Water Act (CWA),
which was first passed in 1972, makes it ille-
gal for a factory or another point source to
dump any pollutant in a waterway without
a permit. The CWA also sets standards for
industrial wastewater management, places
restrictions on wetland destruction or con-
version, and provides funding mechanisms
for upgrading municipal wastewater treat-
ment plants. One interesting provision of
the CWA allows individual citizens and envi-
ronmental groups to monitor and report to
the federal government cases in which CWA
standards are not being met. This has led
to the formation of hundreds of volunteer
water-quality monitoring groups across the country that regularly test and report on water-
quality conditions in their area. Soon after the CWA was passed, the Safe Drinking Water
Act (SDWA) was enacted in 1974. The SDWA required that the EPA set specific standards for
allowable levels of chemicals in water and mandated that local water authorities monitor and
report on drinking water quality in their jurisdictions.

While the CWA and the SDWA have both resulted in dramatic improvements in water quality
in the United States since the 1970s, there remain significant challenges with water pollu-
tion, particularly from nonpoint sources. (If you’re interested in the quality of your own local
water supply, check out Close to Home: Assessing Local Drinking Water.) The remainder of this
chapter will focus on additional approaches both to conserve water and manage demand, as
well as on further ways in which water quality can be protected. This includes a discussion of
water conservation and management in Section 5.6 and the role that forests play in protecting
water supplies in Section 5.7.

Aaron Bacall/Cartoon Collections

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171

Section 5.5 Water Quality

Close to Home: Assessing Local Drinking Water

The Flint water crisis began in 2014 when the city of Flint, Michigan, changed its public
water sources from the Detroit River and Lake Huron to the Flint River. During the transition,
the city mismanaged how it was treating its water, and pipelines began releasing large
amounts of lead into the public water supply. More than 100,000 residents were exposed
to high levels of this heavy metal neurotoxin, including 6,000 to 12,000 children who may
suffer from lifelong health challenges as a result. A federal state of emergency was declared
in 2016, and ever since, officials have been scrambling to fix the problem.

The Flint water crisis demonstrates the high stakes involved with protecting public water
supplies. It also highlights the importance of regular water monitoring. In this feature box,
we will learn about some regulations that protect our water supplies. We will also take a
closer look at where our drinking water comes from and determine if it is safe to drink.

The SDWA of 1974 requires the mandatory monitoring of public water supplies throughout
the United States. Local water authorities must test drinking water for microorganisms,
disinfectants, and chemical pollutants like lead on an annual basis and publish their findings
in documents called Consumer Confidence Reports (CCRs). These reports provide background
information on local water systems as well as the detailed monitoring information of specific
pollutants. Table 5.4 is an excerpt from a 2017 CCR for Meadville, Pennsylvania.

(continued)

Table 5.4: Excerpted 2017 water test results for Meadville, Pennsylvania

Con-
tami-
nant

Action
level MCLG

90th
per-
centile
value Units

Sample
date

# of
sites
above
AL of
total
sites

Viola-
tion

Sources of con-
tamination

Lead 15 0 2 ppb 06/01/16 0 out
of 30
sites

No Corrosion of
household
plumbing; ero-
sion of natural
deposits

Copper 1.3 1.3 0.5 ppm 06/01/16 0 out
of 30
sites

No Corrosion of
household
plumbing; ero-
sion of natural
deposits; leach-
ing from wood
preservatives

Source: From “2017 Annual Water Quality Report,” by Meadville Area Water Authority, 2017 (https://meadvillepa
water.govoffice3.com/vertical/Sites/%7BEB63EC2C-4A5A-4CE9-8231-28BBB646C55F%7D/uploads/2017_Consumer
_Confidence_Report.pdf ).

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172

Section 5.6 Water Conservation and Management

5.6 Water Conservation and Management

Throughout the 20th century, the primary approach to meeting growing water needs and
demand was to build more dams, reservoirs, pipelines, and water treatment plants. The basic
idea was to deliver high-quality water to all end users and to eliminate wastewater. The result
was a highly centralized and industrial-scale approach to meeting water demand, one that
placed a large amount of political and economic power in the hands of water utilities.

Peter Gleick, a water scientist and cofounder of the Pacific Institute, has labeled this approach
the hard path for water because of its focus on physical infrastructure and water supply
projects. While Gleick acknowledges that hard path approaches have brought economic and
health benefits over the past 100-plus years, he argues that now is the time for a new approach
to water management. This new approach, a soft path for water, is meant to complement
and build on the success of established hard path infrastructure. But rather than building
new water supply and distribution systems, the soft path focuses on improving efficiency
and helping local communities take control of their own water needs (Gleick, 2010; Pacific
Institute Staff, 2013).

Close to Home: Assessing Local Drinking Water (continued)

This section of Meadville’s CCR presents the results of lead and copper monitoring. Three
columns, in particular, provide important information about the safety of this drinking water.
First, there is the maximum contaminant level goal (MCLG) for each pollutant. Depending on
the type of pollutant being measured, these values might also be called a maximum residual
disinfectant level goal (MRDLG). When pollutant levels are below these values, there is no
known risk to human health.

You may also notice the column providing an action level (AL) for each pollutant. This value
represents the enforceable standard for drinking water. In other words, the EPA requires
water authorities to take action when measurements exceed these levels. These levels may
also be listed on CCRs as maximum contaminant levels (MCLs) or a maximum residual
disinfectant levels (MRDLs). In general, these values are set as close to MCLGs and MRDLGs
as possible while taking technology and cost limitations into consideration.

Finally, the column labeled “# of sites above AL of total sites” tells us how many of the
locations sampled by the water authority exceeded the upper limits set by the government.
Luckily for the folks in Meadville, none of these sites appeared to have excessive amounts of
lead or copper.

Now that you have a better understanding of what drinking water information is available
and what it means, see if you can find a CCR for your location. You can often find them on the
Internet by using “Consumer Confidence Report” and the name of your hometown as search
terms. You can also obtain this information by reaching out to your local water authority. By
reading the CCR for your hometown, you will learn a little bit more about where your water
comes from and whether there are any contamination issues you should be concerned about.

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173

Section 5.6 Water Conservation and Management

Characteristics of the Soft Path
Gleick distinguishes the soft path for water from the hard path in a few different ways. First,
the soft path focuses on meeting the water-related needs of people, not just a certain level of
supply. People need water to clean clothes, irrigate crops, and shower, and if we can help them
find a way to do these things with less water, we should. For example, washing machines that
use half the water to wash clothes or irrigation systems that require one third of the water to
support crops are still allowing home owners and farmers to achieve the desired outcome at
a lower cost.

Second, the soft path pays more attention to matching water quality to specific end uses. For
example, water for irrigation or certain industrial uses does not have to be of the same quality
as water we use for drinking or bathing. As a result, soft path approaches often involve finding
ways to reuse water more than once before treating it, such as by diverting gray water—rela-
tively clean water from sinks and showers—to water plants or flush toilets.

Third, the soft path emphasizes smaller, decentralized solutions to water management issues.
Rather than invest massive amounts of scarce capital in new water supply systems, these
funds could be used to pay for hundreds of smaller scale initiatives at the local level that save
just as much or more water. For example, many water utilities promote and even make avail-
able, at low cost or no cost, water-conserving devices (such as low-flow showerheads and
rain barrels) and products to their customers.

Fourth, the soft path recognizes that water is as essential to the health of natural systems as it
is to human society. Therefore, soft path approaches seek to work with nature rather than try-
ing to engineer or work against it. This is precisely what New York City did when it invested
in the water purifying ecosystems in its water supply region.

Examples of the Soft Path
Soft path approaches to water management are becoming more common as opportunities
to develop new water supplies dwindle and as the cost of hard path approaches continues to
rise. In the 1970s Orange County, California, was one of the first locations in the United States
to experiment with treated wastewater reuse. At the time, the Orange County Water District
was pumping water out of its main aquifer faster than it could recharge, and as a result salt
water from the nearby Pacific Ocean was seeping into the aquifer. The water district also
imported water from the Colorado River and the Sierra Nevada mountain range, but that sup-
ply was limited and costly. A decision was made to take municipal wastewater—the water left
over after sewage is treated—and pump it into holding ponds directly above the municipal
aquifer. This wastewater slowly seeps into the aquifer below, which helps maintain water lev-
els and supply. Because soil can naturally filter any remaining contaminants from the water,
this approach also maintains the quality of Orange County’s main aquifer. Orange County’s
wastewater-to-drinking-water facility (known as the Groundwater Replenishment System) is
now the world’s largest, and with an upcoming expansion scheduled to begin in late 2019, it
will provide close to 500 million liters (130 million gallons) of drinking water a day and meet
40% of the district’s overall demand.

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174

Section 5.6 Water Conservation and Management

In addition to wastewater reuse, local water authorities are adopting other soft path
approaches. For example, Los Angeles and other cities in Southern California used to try to
prevent flooding by building concrete drainage channels to carry storm water straight to the
ocean. Today these cities are making changes to road surfaces, city parks, and other built-up
areas to slow storm water runoff and increase rates of recharge to underground aquifers.
These are examples of the soft path approach of working with nature.

Cities in the eastern United States that have older water distribution systems are increasing
efforts aimed at leak detection and repair. The WRI estimates that up to 50% of all the water
“captured” by water supply systems in the United States is lost to evaporation, leaks, and
inefficient use. Basic investments in leak detection and repair can cut these losses dramati-
cally and save water districts and their customers millions of dollars. Elsewhere, especially in
drought-prone regions of the Southwest, water districts are working with local residents to
help them cut water use for landscaping, bathing, toilets, and other purposes (see Figure 5.8).
It costs the water district less to help a customer cut water demand than it does for the water
district to increase water supply.

Given that agriculture is the single biggest user of water globally, improving water use effi-
ciency in this sector is an important part of the soft path approach. The most basic and inef-
ficient form of crop irrigation is known as flood irrigation. This involves pumping water from
a river or underground aquifer and allowing it to flow across a farm field. Likewise, spray
irrigation uses large-scale sprinklers to spray large amounts of water on a field. Both methods
lose as much as half the water they spread through evaporation and runoff. Far more efficient
methods for crop irrigation are available and have come into wider use in recent years as
farmers become more aware of water supply challenges. Low-energy, precision application
sprinklers, drip irrigation systems, and center-pivot, low-pressure sprinklers all deliver 80%
to 95% of the water used to the plants where they need it. Small-scale farmers in develop-
ing countries are also increasingly returning to water conservation practices and approaches
that were once more common. These include rainwater harvesting and the construction of
simple “check dams” built across water channels to slow runoff and increase water infiltra-
tion to aquifers. Even small improvements in the efficiency of water use in agriculture can go
a long way to help free up water supplies for thirsty cities like Cape Town, South Africa.

Learn More: Orange County’s Soft Path Approach

More information about the innovative groundwater replenishment system in Orange
County, California, can be found here.

• https://www.ocwd.com/what-we-do/water-reuse
• https://www.ocwd.com/gwrs

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175

Section 5.6 Water Conservation and Management

Figure 5.8: Water efficiency tips

Where else can you save water?

Source: Adapted from artisticco/iStock/Getty Images Plus

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176

Section 5.7 Forests and Water Management

Soft path approaches to meeting water demand represent a move toward integrated water
resources management (IWRM). IWRM looks at issues of water supply and water demand
holistically and in an integrated manner, rather than treating them as separate matters to be
addressed by different agencies and organizations. What soft path approaches and IWRM
have in common is that they tend to put more emphasis on local solutions to local challenges,
rather than relying, for example, on the construction of new dams hundreds of miles away to
meet water supply shortages. Given the increasing challenge of meeting world water needs in
a time of rising populations and global climate change, such local approaches may be the best
option for avoiding severe water shortages and conflict.

The final section of this chapter shifts to a focus on the role of forests and forest ecosystems in
maintaining both water quantity and water quality. As we saw with the example of New York
City’s water system, forested ecosystems help replenish water sources and purify water as it
enters reservoirs, rivers, and streams.

5.7 Forests and Water Management

It may seem odd to have a section on forests in a chapter on water, but effective forest man-
agement plays a critical role in good water management. Forests provide ecosystem functions
and services that affect both water quality and water quantity. In a sense, forests are a form of
natural infrastructure that can be just as important—or even more important—to water qual-
ity and quantity as the physical infrastructure of dams, pipelines, and water treatment plants.

Maintaining Water Quantity
As rains fall and snow melts, forests help slow the rate at which water runs off the surface.
Tree roots and dead branches and leaves on the ground intercept water and hold it, allowing it
to slowly seep into the ground. Some of this water recharges underground aquifers, while the
rest is slowly released into nearby streams and riv-
ers. Experiments at the Hubbard Brook Experimen-
tal Forest in New Hampshire and at other locations
have been designed to measure what happens to
stream flow when forests are cleared (Franz, 2016).
In one experiment after another, water runoff and
stream flow increased dramatically after trees
were removed, resulting in a stream flow pattern
that spikes immediately after rains or snow melt
(increasing the risk of floods) and then drops dra-
matically soon after. In contrast, when forests are
intact, water from rains and snow melt is released
slowly to underground aquifers and nearby streams,
and stream flow patterns are more steady and reli-
able. In fact, it’s typically the case that even after
weeks of no rain or precipitation, forest streams are
still flowing with significant volumes of water.

iStock/Thinkstock
Cleared forest land—such as the
deforestation in the Amazon shown
here—can create sediment loading in
nearby streams and rivers, creating
water-quality issues for communities
farther downstream.

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177

Section 5.7 Forests and Water Management

Maintaining Water Quality
In addition to maintaining water quantity, forests also help maintain water quality. The Hub-
bard Brook experiments have shown that water running off cleared forest land is high in
nitrates and other pollutants and does not meet clean drinking water standards. Clearing for-
ests also increases soil erosion and “sediment-loading” of streams and rivers, increasing the
costs of water treatment for downstream communities. In contrast, intact forests help pre-
vent soil erosion and can also help trap and hold other pollutants and contaminants before
they can enter nearby waters. This is why riparian buffers—discussed in Section 5.5—are so
important to water quality.

The example of New York City’s water system at the start of this chapter helps illustrate the
importance of forests in good water management. Another example comes from Rio de Janeiro
in Brazil, site of the 2016 Summer Olympics. Rio operates the world’s largest water treatment
plant to provide clean water to its 6.3 million residents. However, this treatment facility is
facing operating challenges due to deforestation that is occurring upstream from the city.
The deforestation is increasing rates of soil erosion and leading to increased sediment in the
water as it reaches Rio’s reservoirs. Like New York, Rio is approaching this challenge not by
constructing more or better water treatment plants but by going to the source of the problem
in upstream watersheds. The strategy is to restore and maintain upstream forested areas, an
approach that will save the city an estimated $79 million in water treatment costs annually
while also improving water quality (Ozment & Feltran-Barbieri, 2018).

Maintaining the Global Water Cycle
In addition to their direct and immediate impact on water quality and quantity in nearby eco-
systems, we are also becoming more aware of the critical role that forests play in maintaining
the global water cycle. Trees and other plants perform the ecosystem service of drawing water
from the soil and releasing it to the atmosphere as water vapor through transpiration. This
process has been summed up beautifully by environmental journalist Fred Pearce (2018a):

Every tree in the forest is a fountain, sucking water out of the ground through
its roots and releasing water vapor into the atmosphere through pores in its foli-
age. In their billions, they create giant rivers of water in the air—rivers that form
clouds and create rainfall hundreds or even thousands of miles away. (para. 1)

Those “giant rivers of water in the air” are disrupted through deforestation, especially large-
scale tropical deforestation. Deforestation in the Amazon basin could disrupt precipitation
patterns and agriculture in China and central Asia thousands of miles away.

As a result, any discussion of effective and sustainable water management should also include
ideas for sustainable forest management. In forested, tropical regions of South America,
Africa, and Southeast Asia, this often involves efforts at community-based forest manage-
ment. Rather than fencing off forests as a means of protecting them, these programs work
with local communities to help them derive a livelihood from the forests while also managing
them sustainably. Rain forest–certified coffee, chocolate, and other products are examples of
items that can be produced in a way that maintains the ecological integrity and ecosystem
services of forested regions.

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178

Bringing It All Together

Bringing It All Together

It’s somewhat remarkable that water is so essential to human life yet many of us barely even
think of it. We turn on the tap or shower, flush the toilet, and consume water-intensive fruits
and vegetables with barely a thought to where that water came from or where it goes after
we use it. This is partly a function of where and how we live. For example, where this book’s
authors live in northwestern Pennsylvania, it seems like sometimes there is too much water.
As a result, it can be hard to appreciate notions of water as “scarce” or “precious.” In con-
trast, residents of places like California and Cape Town, South Africa, who have lived through
years of crippling drought and water shortages, are more likely to pay closer attention to
their own water use patterns. Even more so, a woman or young girl in a water-scarce or
water-stressed region of the developing world will be acutely aware of the value of water if
she has to walk long distances every day to acquire it.

Despite an evolving awareness and growing evidence of the challenges of meeting water
demands in a time of population growth and global climate change, we are still largely
approaching water and forest management in ways that are problematic. Hard path
approaches that dominated water management throughout the 20th century are bumping
up against physical, financial, and ecological limits. Soft path approaches are becoming more
widely adopted but perhaps not as quickly as needed. A more rapid move toward soft path
and integrated water resource management approaches is called for, one that looks at issues
of water supply, demand, access and human rights, ecosystem management, and trans-
boundary political cooperation as interconnected rather than separate.

While this chapter dealt with that small portion of the planet’s water that is fresh, the next
chapter will examine the challenges of sustaining the oceans that cover over 70% of the
Earth’s surface. We will see, perhaps not surprisingly, that some of the same issues that
make management of freshwater resources a challenge also apply to the oceans. We’ll also
see that a growing awareness of the importance of oceans to all life is driving innovative
approaches to sustaining this remarkable and vast resource.

Additional Resources

Global Water Use and Demand

The Yale Environment 360 website features an excellent five-part series, “Crisis on the
Colorado,” that examines the threats to the Colorado River system and the communities that
depend on its water.

• https://e360.yale.edu/series/crisis-on-the-colorado

National Public Radio featured a series of stories called “Stories From the Water Front” that
focused on communities struggling with water supply and water-quality issues.

• https://www.npr.org/series/646816049/stories-from-the-water-front

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179

Bringing It All Together

There are a number of interesting TED Talks on water shortages. Here are some good
examples.

• Balsher Singh Sindhu: Are We Running Out of Clean Water?:

• Anu Sridharan: When Will I Get My Water Next?:

• Kala Fleming: Easing Water Scarcity by Understanding When and Where It Flows:

The World Resources Institute is an excellent source for information on global water issues.

• https://www.wri.org/our-work/topics/water

The New York Times has a stunning video essay on how global warming is causing glaciers to
retreat in central Asia and what that will mean for local water supply.

• https://www.nytimes.com/interactive/2019/04/17/climate/melting-glaciers
-globally.html

Water and Global Politics

The issue of water shortages and the possibility of conflict between nations over water sup-
plies is growing in importance. These sources take a look at potential cases of water conflict
and what might be done to avoid them.

• https://e360.yale.edu/features/mideast_water_wars_in_iraq_a_battle_for
_control_of_water

• http://worldwater.org/wp-content/uploads/2013/07/www8-water-conf lict
-events-trends-analysis.pdf

• http://worldwater.org/wp-content/uploads/2013/07/ww8-ch1-us-water
-policy.pdf

• https://www.wri.org/blog/2018/11/un-security-council-examines-connection
-between-water-risk-and-political-conf lict

Water Quality

In a humorous TED Talk, Rose George talks about the issue of a basic, sanitary toilet and the
implications for water quality.

• https://www.youtube.com/watch?v=ZmSF9gVz9pg

Water Conservation and Management

In this TED Talk, Lana Mazahreh talks about water conservation lessons learned while grow-
ing up in Jordan.

• https://www.youtube.com/watch?v=nLB8A–QdHc

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180

Bringing It All Together

As water shortages become more widespread and severe, there is increasing interest in the
idea of developing “toilet-to-tap” schemes that would purify and reuse water from toilets
and other water washed down the drain. This water is variously known as “gray water” if
it’s from sinks or showers and “brown water” or “black water” if it’s from toilets. As much
as people are taken aback by the idea of “toilet-to-tap,” plans are underway to do just that in
cities around the world, including San Diego, California.

• https://www.mnn.com/lifestyle/recycling/blogs/taste-recycled-waste-water
• https://sites.sandiego.edu/sdpollutiontrackers/2018/05/09/toilet-to-tap-not-as

-horrendous-as-youd-think
• https://www.kusi.com/toilet-tap-moving-ahead-san-diego?
• http://www.bbc.com/future/story/20160105-why-we-will-all-one-day-drink

-recycled-wastewater?
• https://www.sciencedaily.com/releases/2018/03/180313084219.htm

Forests and Water Management

The connection between forests and water is the focus of these sites.

• https://www.americanforests.org/blog/the-important-relationship-between
-forests-and-water

• http://www.fao.org/3/a1598e/a1598e02.htm
• https://www.srs.fs.usda.gov/cifs/research/forests-and-water

Key Terms
aquifer An area of permeable rock and
sediment from which water can be extracted.

Clean Water Act (CWA) U.S. legislation
passed in 1972 that makes it illegal for a
factory or another point source to dump any
pollutant in a waterway without a permit.

community-based forest
management Programs that work
with local communities to help them
derive a livelihood from forests while
managing them sustainably.

consumptive use An extractive use
of water that involves withdrawing
the water and using it without
returning it to its source.

ecosystem management In the case
of water, an approach that focuses on
maintaining water quality at the source
rather than cleaning it at its destination.

evapotranspiration The process of
evaporation and transpiration together.

extractive uses The ways water
is used in which it is physically
removed from its source.

hard path for water A term coined
by water scientist Peter Gleick for the
traditional, centralized, and industrial-scale
water management approach. It typically
involves building distant dams, reservoirs,
pipelines, and water treatment plants.

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181

Bringing It All Together

hydrologic cycle The movement of
water between the planet’s surface,
atmosphere, soil, oceans, and living
organisms. Also known as the water cycle.

infiltration The process by which water
sinks slowly down through the soil.

instream uses The ways water is used in
which it is not removed from its source.

nonconsumptive use An extractive use
of water that involves withdrawing the
water and returning it to its source.

nonpoint sources Indirect and
diffuse sources of water pollutants.

point sources Stationary and fixed
sources of water pollutants.

reliable surface runoff Freshwater
runoff that is readily accessible for
human use and consumption.

riparian buffer A vegetated strip of
land alongside a stream or river.

Safe Drinking Water Act (SDWA) U.S.
legislation passed in 1974 that requires
that the EPA set specific standards for
allowable levels of chemicals in water
and mandates that local water authorities
monitor and report on drinking water
quality in their jurisdictions.

saltwater intrusion The movement of
saltwater into freshwater aquifers.

soft path for water A term coined
by water scientist Peter Gleick for an
alternative approach to water management.
It emphasizes improving efficiency and
local solutions over building new water
supply and distribution systems.

surface water Water on the
surface of the Earth, found in rivers,
wetlands, lakes, or reservoirs.

virtual water The water required
to produce a product or item before
it reaches the consumer. Also
known as embodied water.

water scarcity A physical lack of water.

watershed An area of land where
sources of water (streams, creeks) flow
together to a single destination.

water stress A lack of accessible
or affordable clean water.

water table A depth below
ground where soil and rock are
completely saturated with water.

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