The Effect of Global Climate Change on Water Resources............. Tiffany Jebson
Introduction
This chapter examines how water availability and quality may be affected by climate
change within the next century. Throughout this paper, five unique locations—the
western region of continental United States, The West Bank, Tasmania, Bangladesh, and
the Rhine River Basin—will be investigated in reference to water quality and its
capability of supporting and accommodating human life.
Freshwater is a necessity of human survival, and it is therefore important to
understand how global climate change might affect availability of water resources in the
future (EPA, 2009). As the global climate increases, concerns arise: water quality may
decrease as evaporation and transpiration increases; clean freshwater may become less
readily available as population increases; and, human immune system activity may slow
as bacteria thrive in warm water (Justus, et al. 2006). This paper addresses these concerns
and other issues dealing with water sustainability and water quality.
Water sustainability is the capability of water to support and maintain human life
(Weber. 2005). In combination with population growth, climate change may affect water
sustainability throughout the world. In this study, the effect of climate change on water
resources in several areas—the western region of continental United States, The West
Bank, Tasmania, Bangladesh, and the Rhine River Basin—is examined. These locations
were chosen due to their unique geography, climates, and potential for climate change.
For example, some areas of western United States obtain a large portion of freshwater
from snowmelt (USGS. 2011). Figure 1 shows the correlation between snowmelt and
streamflow. During peak times for snowfall and snowmelt, streamflow is high and in the
summer months the streamflow is low. While global climate increase will initially
promote more snowmelt, temperature increase may limit the amount of future snowfall
(USGS. 2011).
Figure 1. Hydrograph which shows daily mean streamflow (average streamflow for each day)
for four years for the North Fork American River at North Fork Dam in California (USGS realtime streamflow data). http://ga.water.usgs.gov/edu/watercyclesnowmelt.html
For the purposes of this study, water quality is defined by the physical, chemical,
and biological properties of water. More specifically, the term deals with water having
the ability to be ingested, be applied agriculturally, and used by humans without any
harmful effects—long-term or short-term.
This paper will explain consequences and benefits of climate change in reference
to global water resources, and it will analyze specific areas in reference to their current
climate and how their water resources might change.
Consequences of Climate Change on Water Supply
This section provides information about potential hazards and concerns regarding
the impact of climate change on the availability and quality of freshwater. For example,
when water quality is compromised, human health may be at risk; lack of freshwater in
the form of precipitation may diminish crop yield; and, higher temperatures cause algal
blooms, which may lead to areas of diminished oxygen. This section will deal
specifically with issues concerning groundwater, weather patterns, algal blooms, hygiene,
and pollutants.
Groundwater: As climate change occurs, the water table, or the surface where the
water pressure is equal to the atmospheric pressure, may lower as temperature increases
cause clouds to retain more water. As the water table lowers to deeper levels, water wells
must be drilled deeper in order to access the groundwater. This may pose a problem as
drilling deeper is more expensive and requires specialized equipment not readily
available. In addition, deeper water wells may reduce groundwater recharge.
Groundwater recharge refers to the process of surface water infiltrating the surface,
moving downward, and reaching the level in which the groundwater was before pumping.
Groundwater recharge can be induced by humans—for example, septic system
drain fields—or occur naturally via precipitation. A 15% reduction in precipitation has
been shown to drastically slow groundwater recharge by as much as 40-50% (Sandstrom,
1995).
Another issue, in addition to the reduction in recharge, is a potential increase in
groundwater discharge. Groundwater discharge is the process of water moving upward
from an aquifer to the surface or atmosphere. Similar to groundwater recharge, this
process occurs either artificially or naturally. Increased groundwater discharge can be
problematic, as it may cause sea level to rise due to the large amounts of water stored in
the ground being released and eventually ending up in the ocean (Sahagian et al., 1994).
Sea level rise may affect approximately one quarter of the world’s population who live in
Figure 2. Groundwater recharge and infiltration.
http://www.wellaware.ca/pages/GroundWater.php
a coastal region. These regions contain only 10% of the global renewable water supply,
and an increase in high salinity water may diminish already-limited freshwater sources
(Kundzewicz et al., 2007). Figure 2 shows the cycle of groundwater recharge and
discharge via infiltration and percolation, or the movement of water through a medium.
Another concern pertaining to drilling deeper wells is that the salinity and
temperature of groundwater may increase, resulting in a lower quality of water. This is
called saltwater intrusion, the movement of saline water to bodies of freshwater.
Weather Patterns: An increase in temperature poses many concerns regarding the
availability of freshwater for human consumption and use. Climate change may
drastically alter precipitation patterns globally. For example, climate change may increase
rainfall in areas of northern latitudes and the tropics, while decreasing rainfall in areas of
lower–mid latitudes (CCSP, 2008). In 2011, Green et al. published a paper modeling the
global changes in mean annual precipitation, evaporation, soil water content, and runoff
for the years 2080–2099. It was estimated that precipitation over land would increase by
about 5%, and precipitation over the ocean would increase by 4%. This estimated
increase in average rainfall was attributed to a proposed increase in water availability
within clouds as they increase in temperature (Green et al. 2011). Similarly, average
evaporation was projected to increase over the ocean with variations related to surface
warming. Over terrestrial areas,
rainfall changes tend to be
controlled by both
evapotranspiration (ET), a term
used to combine total evaporation
and transpiration, and runoff.
Evapotranspiration is illustrated in
Figure 3. For example, average
Figure 3. Diagram of Evapotranspiration.
http://www.westone.wa.gov.au/toolbox6/hort6/html/re
sources/visitor_centre/fact_sheets/images/et.jpg
runoff will decrease in southern
Europe and increase in Southeast Asia
and areas with high latitudes (Meehl,
et al. 2007).
The increase in runoff may lead to higher soil moisture content as well as
unpredictable runoff patterns. As a result of this changing runoff, flooding may ensue.
Flooding may cause problems in overflowing sewer systems, releasing toxins into the
groundwater. Furthermore, some of these toxins may be bacterial in composition, and if
allowed to flow into surface water, eutrophication, a term describing excessive nutrient
content in water, may occur—promoting too much algae growth.
Algal Blooms: Warmer temperatures create an environment in which algae
thrives. Algal blooms will grow rapidly and deplete available oxygen in surface waters.
Areas where this occurs are known as “hypoxic zones” (Osterman, 2009). Hypoxic zones
occur in oxygen-depleted areas that are density stratified, usually thermally controlled,
and combined with a high amount of nutrients. Neither plant nor animal life can sustain
in hypoxic zones.
Algal blooms may also be responsible for compromising animal health, including
that of birds and fish. According to the World Health Organization, the most common
ways humans are affected by algal blooms are via drinking water and recreational
activities. For example, swimming in the vicinity of algal blooms may lead to accidental
ingestion. Side effects of accidental ingestion are vomiting, liver disease, blistering and
skin irritation.
Hygiene: An increase in poor hygiene is another factor that may become a
potential health hazard. Without clean water, viruses and many types of diseases may
spread rapidly. With the continual ingestion of contaminated water, immune system
Figure 4. Map of improved water sources. (WHO, 2008.)
activity slows. Lagging immune systems, caused by contaminated water, is responsible
for over two million child deaths each year (Prüss-Üstün, 2008). The World Health
Organization, in partnership with UNICEF Joint Monitoring Programme, estimates that
1.1 billion people do not currently have access to clean water. If freshwater becomes less
available due to climate change, more people may lose access. This is especially true in
areas that lack improved water sources, or water sources that are designed to provide safe
and useable water. Figure 4 shows the percentage of people that have access to clean
water.
Countries with higher population growth, such as India and China, have less
access to improved water sources.
Pollutants: A pollutant is defined as a substance that is present in concentrations
that may harm living organisms or exceed an environmental quality standard. The term
is frequently used synonymously with contaminant. The United States Environmental
Protection Agency (EPA) has put certain drinking water standards in place to inform
citizens about potential pollutants. Testing parameters include nitrogen, mercury, arsenic,
fecal coliform (E. Coli), and many other chemical and biological constituents. These
constituents are essential to the quality assurance of water, and if consumed in amounts
greater than the EPA standards, these pollutants may prove hazardous.
As the amount of groundwater decreases due to soil evaporation, pollutants that
are already present in the water become more concentrated (Backlund et al. 2008).
Higher concentrations of unwanted chemical constituents may lead to lower quality
freshwater. In addition, using water of a different chemical composition will affect
applications in which the water can be used. For example, water with a high salinity may
only be used in industrial settings, as it is deemed non-potable. In addition, high salinity
waters have a higher density, which may limit use in steam-driven turbines for the
manufacturing of energy (Jonas. 1984).
While it is clear the climate change may have negative effects on water supply
and quality, in some cases climate change may improve water supply and/or quality. As
temperature increases, especially in northern latitudes characterized by snow-covered
terrain, snowmelt may increase. Although a higher amount of snowmelt may increase the
chance of flooding, the excess runoff may provide more water to infiltrate groundwater
aquifers (Green et al. 2011). Groundwater is dominantly controlled by precipitation—
rather than by temperature—making it less susceptible to climate change than other water
sources.
Some Specific Examples
Western United States: The climate in the western region of the United States
shown in yellow in Figure 5—is arid to semi-arid. This portion of the U.S. averages
approximately 400mm of annual
precipitation;
however, this number does vary
significantly with elevation (CCPS, 2008).
Average precipitation in the Western U.S. is
relatively low compared to the eastern region,
which averages approximately 1100 mm of
precipitation annually.
Figure 5. Map of Western Region of United States.
http://www.mytowagent.com/images/map.gif
Freshwater from this region is
mainly obtained from streams that
have been altered by reservoir
management. Much of the runoff in this area is directly sourced from snowmelt, which
may be diminished with climate change. (Talk more about naturally occurring
constituents).
Groundwater aquifers in this region are dependent on the type of geologic features
and rock types present. For example, in the eastern section of this area, the subsurface is
made up of sedimentary rocks. Generally, sedimentary rocks, such as sandstone and welljointed limestone, compose the most effective aquifers. Moving inland, the subsurface is
made up of igneous and metamorphic rocks, which have visible outcrops along the Rocky
Mountains. Igneous and metamorphic rocks are not usually great aquifers unless they are
faulted, which creates space for groundwater to occupy.
The West Bank: The West Banks is
located in the Middle East, near the
Mediterranean Sea, as shown by Figure 6.
The landscape of the West Banks can be
divided into three distinct locations: the west,
an area characterized by plains, the central
mountainous area, and the Jordan Rift valley
in the east. The climate for this area is
Figure 6. Map of the West Bank.
http://israelipalestinian.procon.org/files/IsPal%20I
mages/westbank.jpg
temperate; temperature and
precipitation vary with elevation, has warm to hot summers, and cool to mild winters.
Although there are three distinct regions, negative effects will be averaged to create a
single scenario for The West Bank. Droughts are the biggest natural disaster that affects
the West Bank and issues with sewage treatment as well as adequacy of freshwater are
problematic. Agriculture occupies 5% of cultivated land but utilizes approximately 52%
of the available water resources (Mizyed. 2008). An estimated 2.3 million people live in
the West Bank. The expected growth rate for the West Bank is between three and four
percent.
Freshwater is this area is obtained mostly from groundwater aquifers. Irrigation is
prevalent in this area due to lack of surface bodies of water.
The temperature increase in the West Bank is estimated to be from 1.7 to 6.5
degrees Celsius (Mizyed. 2008). From Mizyed, published in 2008, it is expected that an
increase in temperature may cause a six to seven percent increase in evapotranspiration.
The Sandstrom paper, published in 1995, estimates that this area may experience
approximately 16% loss in precipitation that could result in as much as a 30% decrease in
the groundwater recharge rate. With the location of the West Bank being in an area of
political conflict, shortages in water may escalate existing tensions between different
extremist groups.
=Tasmania, Australia: Located in the Pacific Ocean, shown by Figure 7,
Tasmania is an island approximately 240 km south of mainland Australia. Tasmania has a
maritime climate, meaning mild winters and warm summers with high annual rainfall.
Approximately 50% of Tasmania is native vegetation, 22% is forestry, 22% is grazing,
and 2% is irrigated agriculture (Post et al. 2012). The population is approximately
510,560 people and has a 0.33% growth
rate. Average rainfall for Tasmania is
approximately 1266mm annually.
However, there is a large discrepancy
between rainfall of the east and west
coasts of Tasmania. The west coast
usually receives approximately 4200mm
of rain annually, whereas the east coast
receives only 700mm (Post et al. 2012).
Using different models for
Figure 7. Map of Tasmania.
http://media.web.britannica.com/eb-media/58/64358-00454829D52.gif
climate change in Tasmania can
yield very different results.
According to a paper written by
Post et al. in 2012, there are three distinct models used when creating future predictions
of water availability. The first model is a wet climate and predicts a 1% increase in
precipitation and 10% increase in groundwater recharge. The second model, representing
the median between wet and dry values, predicts a 2% decrease in precipitation and
yields current recharge rates. The final model, representing a dry scenario predicts a 6%
decrease in rainfall and a 5% decrease in groundwater recharge. Runoff for each of these
scenarios will be directly related to the amount of annual precipitation, increasing with
precipitation.
Bangladesh: Bangladesh lies between India and Burma shown on Figure 8 in red.
A humid, warm, tropical climate is characteristic of Bangladesh and is primarily
influenced by monsoon cycles. Bangladesh is used agriculturally and approximately 85%
of its population depends on these agriculture activities. Bangladesh is characterized by
flat plains with occasional hills. Topography as well as geographic location make
Bangladesh prone to natural disasters such as
cyclones, flooding, erosion, tornadoes, droughts, and
Figure 8. Map of Bangladesh.
http://world.unomaha.edu/files/Image/cropped%2
0bangladesh_map.jpg
earthquakes (Agrawala et al. 2003). Approximately
151,000,000 people live in Bangladesh with a 2%
growth rate (CIA World Factbook. 2012).
A majority of freshwater for agriculture
comes from tube wells. Tube wells are essentially
what is used in the United States as groundwater
monitoring wells at landfill sites. A schematic
diagram of a tube well is illustrated in Figure 9. Tube
wells are lined with a polyvinyl chloride (PVC) pipe
and have a screened interval at the bottom portion of the well. Gravel and a type of clay
called Bentonite line the well as a natural screen and deterrent for large particles. When a
well is installed, it needs to be developed. This means that water must be purged from the
well until it is clear. Since the well was not dewatered during installation it may contain
sediment and other particulate matter.
Hossain et al. published in 2011, uses current water table data and trends to model
future water availability. Depth to water table
may double around the year 2060. This will
increase pumping costs and environmental
problems may arise, which is common for
deeper drilled water wells. Overuse of
groundwater is occurring and pumping has
already surpassed the recharge rate, therefore
lowering the water table indefinitely.
According to Agrawala et al. 2003,
cyclone frequency is modeled. Peak
intensities of cyclones are predicted to
increase by 5-10% and precipitation is
expected to increase by about 20-30%.
Figure 9. Schematic Diagram of Tube Well.
http://www.fhwa.dot.gov/bridge/tunnel/pubs/nhi09010/images/
fig_15_29.gif
This will increase the risk for flooding, which Bangladesh is already prone to. Another
risk for Bangladesh is sea level rise. Bangladesh is a low-lying country and any changes
to sea level will greatly affect Bangaladesh. Furthermore, saltwater intrusion may also be
another imminent threat.
Rhine River Basin, Europe: The Rhine River, located in Western Europe, is
shown in Figure 10. The Rhine River flows through seven countries and is essential for
hydropower generation, agriculture, industry, and domestic water use. The Rhine River
Basin is highly populated with
many large cities dependent upon
it.
The Rhine River starts in
Swiss Alps and flows downstream
towards the low-lying Netherlands.
Many dams are built along the
Rhine and the swift current allows
for rapid erosion. When the river
reaches the Netherlands, the water
Figure 10. Map of the Rhine River Valley.
http://3.bp.blogspot.com/_A0lijzs4VO4/TJBVwVN7_tI/AAAA
AAAAAK0/BnOdweLIrbQ/s1600/Rhine+River.jpg
begins to slow, creating an
environment that allows rapid
sedimentation (Middelkoop et al. 2001).
Effects from climate change vary along this vast river basin. Middelkoop et al.,
published in 2001, identify the effects on the Rhine River from climate change. In the
alpine region of Switzerland, snow accumulation during the winter months will decrease
which will increase the amount of runoff. Warmer temperatures during the summer will
increase evaporation and precipitation is predicted to increase. However, more
evaporation will occur giving this region a decrease in net runoff water. In the Germanmiddle mountains area, evapotranspiration along with precipitation determine the water
availability. Evapotranspiration is estimated to counterbalance the increase in annual
precipitation, therefore giving this area a net decrease in runoff water. Finally, in the
lowland area of the Rhine River Basin, streamflow is estimated to increase by
approximately 20% due to an increase in precipitation. During the summer months,
evaporation will take up a large portion of water, possibly causing a water deficit for a
portion of the summer.
Conclusion
Using mathematical models and present examples, water sustainability due to
climate change can be investigated. Advancing technology, to more efficiently clean and
distribute freshwater, needs to continue in order to keep up with the growing demand of
clean water. By reducing greenhouse gas emissions and humankind’s carbon footprint,
the adverse effects of climate change may be impeded. More efficient water management
programs need to be initiated. By looking at specific examples, effects on water resources
from climate change can be better understood. The only thing that is certain is that water
is vital and without it, life will not continue.
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