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 specific locations—the
western region of continental United States, The West Bank in the Middle East,
Tasmania, Bangladesh, and the Rhine River Basin—will be investigated in reference to
water quality and its capability of sustaining 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 temperatures increases, concerns arise: water
availability may decrease as evaporation and transpiration increase, 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). Water resources are already being overused and over-pumped. As
population increases problems with overuse may become worse. In this study, the effect
of climate change on water resources in several areas—the western region of continental
United States, The West Bank in the Middle East, Tasmania, Bangladesh, and the Rhine
River Basin—is examined. These locations were chosen due to their specific geography,
climates, and potential for climate change. For example, some areas of the western
United States obtain a large portion of freshwater from snowmelt (USGS. 2011). Figure 1
shows daily streamflow in the Northfork American River at North Fork Dam in
California in years 1998-2002. The high streamflow during the first part of each year is
thought to reflect snowmelt entering the river. During the years 1998-2001, it can be
interpreted that a large amount of snowfall occurred, thus resulting in a larger
streamflow. While a global temperature 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 purpose of this study, water quality is defined by the physical, chemical,
and biological properties of water. More specifically, water quality describes the ability
of water to be ingested, to be applied agriculturally, and to be 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 in response to changing climate.
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 a temperature increase
may cause clouds to retain more water. As the water table lowers to deeper levels,
drinking 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 some areas. In addition, deeper drinking 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 a small rise in sea level due to the large amounts of water
stored in the ground being released and eventually ending up in the ocean (Sahagian et
al., 1994).
Figure 2. Groundwater recharge and infiltration.
http://www.wellaware.ca/pages/GroundWater.php
Sea level rise, due to either an increase in groundwater discharge or melting ice
caps, may affect approximately one quarter of the world’s population who live in 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 approximately 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
Figure 4. Map of improved water sources. (WHO, 2008.)
spread rapidly. With the continual ingestion of contaminated water, immune system
activity slows. Weakened 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 per country 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 (USEPA) 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 available 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 that climate change may have negative effects on water supply
and quality, in some cases climate change may improve the 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 possibly 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 and in some particular places,
temperate. 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.
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.
Mean annual precipitation in this area is predicted to decrease which could mean
less available water in this area. An increase in temperature may also lead to the earlier
melting of snow in the Rocky Mountains. Early spring streamflow of rivers in this area,
may increase due to the snowmelt and average summer streamflow may decrease. Areas
located along the coast may also be at risk for saltwater intrusion, an effect of lowering
water table and slower recharge rates (Bates et al. 2008).
The West Bank: The West Bank 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
temperate; temperature and precipitation vary with elevation, has warm to hot summers,
and cool to mild winters. Although there are
Figure 6. Map of the West Bank.
http://israelipalestinian.procon.org/files/IsPa
l%20Images/westbank.jpg
three distinct regions, climate change 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 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
Figure 7. Map of Tasmania.
http://media.web.britannica.com/eb-media/58/64358004-54829D52.gif
receives only 700mm (Post et al. 2012).
Using different models for 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 predicting future water
availability. The first model represents a wet climate and predicts a 1% increase in
precipitation and a 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. Monsoon cycles are dependent upon wind circulation; air
rising over heated land in summer months creates a
low-pressure system then, comes in contact with a
Figure 8. Map of Bangladesh.
http://world.unomaha.edu/files/Image/cropped%2
0bangladesh_map.jpg
cooler air mass that condenses warm air, thus
creating heavy rainfall. 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 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.
Figure 9. Schematic Diagram of Tube Well.
http://www.fhwa.dot.gov/bridge/tunnel/pubs/nhi09010/images/
fig_15_29.gif
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%. 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
the Swiss Alps and flows
downstream towards the low-lying
Netherlands. Many dams are built
along the Rhine River and the swift
current allows for rapid erosion.
When the river reaches the
Figure 10. Map of the Rhine River Valley.
http://3.bp.blogspot.com/_A0lijzs4VO4/TJBVwVN7_tI/AAAA
AAAAAK0/BnOdweLIrbQ/s1600/Rhine+River.jpg
Netherlands, the water begins to
slow, creating an environment that
allows rapid sedimentation, or the settling of sediment that was suspended (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. With this increase in evaporation, this region may experience a
decrease in net runoff water. In the German-middle mountains area, evapotranspiration
along with precipitation determine the water availability. Evapotranspiration is estimated
to overcompensate 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 given amount of time during 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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