Download Global Warming Impact on Snow-Covered Mountain Ranges and

Spring
12
Faculty Advisor – Todd Royer
School of Public and Environmental
Affairs
Morgan Conway
Increasing temperatures have large effects on the hydrologic cycle, influencing snowmelt, snowpack, stream flow and
water runoff. These are three extremely important factors in the management of water resources. Areas of great
sensitivity to these effects include mid-high altitude mountainous ranges. One reason for this is that most
mountainous areas rely on snowmelt for their main water supply. With increased temperatures due to climate
change, some detrimental effects can be seen in these areas. These include, earlier snowmelt and runoff, more
precipitation in the form of rain and not snow, and changes in flow patterns. This can result in longer dry seasons
with lower water supplies. Areas of high concern include the Western United States, and the basins of the Himalayas,
Andes and Alp regions. Each of these areas has unique concerns based upon their location, but all share water
scarcity as being their biggest concern. Other areas of concern include the economic impacts, as well as an increase
and severity of droughts. The largest concern still remains for domestic and agricultural use of water and finding
adequate reservoir storage to handle the earlier snowmelt and runoff in these areas.
School of Public and Environmental Affairs
Introduction
The effects of climate change can be seen in all parts of the world. Some areas
are more sensitive to the changes in climate due to different topographic features
among other factors. One of the most prominent factors is the region’s hydrologic
cycle. Warmer temperatures have a large effect on the hydrologic cycle, especially in
snowmelt-dominated regions. These effects include snowpack loss, earlier
snowmelt and earlier runoff, as well as impacting the management and storage of
reservoirs. There are four main regions of high concern, which include, the western
United States, the Alps, the Himalayas, and the Andes. As different as these regions
are, water scarcity is a common problem among them all. As warmer temperatures
increase, so does the danger for those who live in these snow-dominated regions
and rely on snowpack or glacier melt for their water supply.
Climate Change
Climate change is happening worldwide and will only increase during the
next decades. It is estimated that by the middle of the century there will be an
increase of temperature by 1-2 degrees Celsius (Cayan, 1996). The increase in
temperature over time can be seen in Figure 1. As shown, temperatures recently
have been reaching levels that far exceed any previous level (Hansen, et al. 2010).
Figure 1 is from J Hansen’s study on Global surface temperature change. Above shows the annual and 5year temperature mean from 1880-2000. In the later part of the 20th century see much higher
temperatures then the 100 years prior.
This increase in temperature not only affects the climate, but many other
systems as well. Some of the main systems affected include the ocean and air,
hydrologic, and biological systems. This translates into the human lifestyle in means
of food, water scarcity and diseases, among others (Pachauri, et al. 2007). The focus
of this paper is on the warming temperatures on the hydrologic cycle. The
temperature increases are not consistent on all regions of the planet. Although it is
predicted to be a global temperature rise of 1-2 degrees Celsius, not all areas will
see exactly that. Some regions may see more, others may see less. The areas that
will see the greatest increase in temperature are those regions in mid-to higher
latitudes (Pachauri, et al. 2007). This accounts for the heavily impacted, snowmeltdominated regions. As shown in Figure 2, areas of higher elevation have the
greatest air temperature change (Bradley, et al. 2006).
Figure 2 "Global Warming in the American Cordillera" The black triangles show the mountains with the
highest elevation at each latitude.
Mountain snowpack is extremely important in the hydrologic cycle for
snowmelt-dominated regions. Snowpack will see some of the most significant
impacts from global warming (Clow, 2010). One of the changes will be size of the
snowpack. As temperatures rise, more precipitation falls as rain instead of snow
leading to smaller snowpack. Also affected by warmer temperatures are glaciers.
Glaciers have a higher rate of melting with higher temperature. This is shown in the
graph below with changes in glacier size coinciding with average summer
temperatures. The graph shows that for the glaciers in Glacier National Park, as the
average temperature increased, the glaciers were retreating at a more rapid pace
(Hall, et al. 2003).
Figure 3 "Changes in glacier size and summer temperature 1850-1995"
As the earth’s air temperature continues to rise, it will have a large effect on
snowmelt-dominated regions and their snowpack. Thus, warmer temperatures will
affect the hydrologic cycle for snowmelt-dominated regions.
Fresh Water
Fresh water is one of the main components to human survival, along side
food and oxygen. Most of the earth’s water supply is located in the oceans;
however, ocean water is not a viable source of drinking water. Only 3% of the total
water supply is fresh water and this fresh water is found in many different forms.
For instance, 2% of that is found in ice. Only .05% of the total water supply is fresh
liquid (Witzel, 2001). Fresh liquid is the water resource used for drinking water.
Most of the world derives their potable drinking water from rivers. In areas of midhigh latitude, snow-dominated regimes, this river water is supplied from the
snowpack melt (Barnett, et al. 2004). These areas rely heavily on the mountain
snowpack for their fresh water. Snow-dominated regions supply the water
resources for many people. Approximately 1/6 of the world’s population lives with
in these regimes (Barnett, et al. 2008). That is roughly 1 billion people that rely on
snowpack or glacier melt for their water. This calculation does not take into account
those that live outside the basins, but rely on the water source from inside the
basins. This makes the number of those impacted even larger. Therefore,
mountains are considered important and a needed source of fresh water worldwide
(Viviroli, et al. 2004).
Globally, humans do not live in proportion to water supply. This can
sometimes lead to areas that have high risk of water resource problems holding an
abundant amount of people (Barnett, et al. 2008). It is because of this that it makes
management of fresh water even more crucial, especially in these areas.
Hydrologic Cycle
The hydrologic cycle determines how humans receive their water. It is the
driver to all water supplies. Depending on location, topography and climate,
different parts of the hydrologic cycle will be more prominent. For snowmeltdominated areas, the hydrologic cycle starts in the mountains.
The first step is precipitation. For these regions, the majority of their
precipitation falls during the winter and spring months as snow. The summer and
autumn months receive significantly less precipitation. The precipitation
accumulates into mountain snowpack. Over time, this snowpack becomes a natural
reservoir for water storage. This snowpack is at its largest at the beginning of the
spring (Cayan, 1996). As the temperature rises, the snow begins to melt. This
creates the next hydrologic step, water runoff. The runoff from the snowpack flows
into the rivers of that basin. This runoff gives the rivers a steady streamflow
throughout the low precipitation months to the mountains basins, providing water
supply in otherwise dry times (Christensen, 2004).
The USGS graph below in Figure 2 shows the stream flow at different times of
the year. It is easy to see the highest point is when the snow is melting and
providing runoff for the river. That is then carried into an elevated stream flow for
the rest of the low precipitation months. Without that snowmelt, the stream flow
would be a lot lower (USGS, 2001).
Figure 4 "USGS Androscoggin River near Auburn, Main" This graph shows the streamflow cycle for a
snowmelt-dominated region
The timing of the snowmelt is an important component in the hydrologic
cycle for a snowmelt-dominated region. That is because the maximum streamflow
months coincide with what would be the lowest baseflow months, if it were not for
the snowmelt at that time. It is also beneficial because the snowmelt then provides
water during the time of maximum heat stress and water demands (Corripio et al.
2006). These are the main reasons why the timing of the snowmelt is so crucial in
the hydrologic cycle of a snow-dominated region, as well as being crucial in the
water availability for the basins.
Understanding the hydrologic cycle for a region is an important component
in the management of water supplies. Fresh water is not an infinite resource, and it
will become even scarcer as temperatures increase. The hydrologic cycle impacts
the availability of water for a given area (Bales, et al. 2006). It is important to
understand the driving factors of the hydrologic cycle, such as temperature. This
impacts when, how and how much water will be available for a region. An
understanding of the areas hydrologic cycle will help manage the resource they
have, as well as help plan for the future.
Infrastructure
Understanding the infrastructure of what supplies the basin with water is
equally as important as understanding the hydrologic cycle. One of the most
important structures in the snowmelt-dominated region’s hydrologic cycle is the
snowpack.
The most important role of the snowpack is that of a reservoir. During the
winter months when precipitation is at it’s highest, the snow accumulates and forms
the snowpack. This accumulation of water, in the form of snow, is a natural
reservoir (Clow, 2010). Since water is in abundance during these months, the
excess is naturally stored in the snowpack. This holds large “water equivalence”
naturally. The snowpack’s capacity as a water storage can be much greater then any
man made reservoir (Clow, 2010). This water is stored all winter long and then
slowly released starting in the spring with snowmelt. In some regions, the water
runoff from mountain snowmelt can account for as much as 95% of the total
streamflow (Viviroli, et al. 2004). The snowpack holds large amounts of water in a
natural storage and is released during the months of need.
One of the major concerns with warmer temperatures is the change in
snowmelt timing. The natural reservoir of snowpack works well for these areas
because it holds and captures the water, and then naturally releases the snowpack
when it is needed. Earlier snowmelt would come at a time of high base flow in the
rivers, when the water is not needed, and would then become excess water. If this
water is not captured or stored, it will continue as excess in the rivers and could
flow straight into the ocean (Barnett, et al. 2005). Once in the ocean, the water is no
longer a form of fresh water and becomes non-potable.
Not only does this change the benefits of the natural reservoir, but it also
requires a change in the management of water. With warmer temperatures
snowmelt is predicated to, in some areas, come as soon as a month earlier then
normal (Barnett, et al. 2008). With this earlier snowmelt, a way of capturing and
storing this earlier runoff is needed. Below is a graph from EOS of the projected
storage required for future temperatures against the current storage required. As is
shown, the projected storage required for the high river flow, is much larger then
the current storage required (EOS, 2009).
Figure 5: Projected storage required verses current storage required give current and project river
flows for different months of the year
In order to handle this change, regions need to adapt. If the hydrology is
changing, regions need to manage their water resources in a way that changes with
that. This can be in the form of creating new reservoirs to handle the earlier
snowmelt and/or more regulation regarding water resources.
Streamflow is another important piece in the infrastructure of the hydrologic
cycle for snowmelt-dominated regions. The streamflow is important because it
provides many things, including water resources and energy. The water resources
include both domestic and industrial water supply, as well as the water for
agriculture. This is what the region relies on for the drinking water, especially in the
more arid and warmer months. The streamflow also provides the energy for the
hydropower (Penderson, et al. 2011). Without the high streamflow during the
summer months from the snowmelt, the energy from hydropower would not be
possible. Lastly, it provides flood control, especially in the higher precipitation
months. Streamflow for snowmelt-dominated basins is reliant on the snowmelt
from the mountains. The basins, in turn, are reliant on streamflow for the water
resource needs.
Case Studies
Rocky Mountains
An example of warming effects on the hydrologic system of a snow-
dominated region can be seen in the western United States. The Rocky Mountain
Range covers many of the states in the west and feds into the Colorado River. This
results in the largest river basin in the area, going through eight states and even
Mexico (Christensen, 2004). Because of this, the water resources in the Colorado
River Basin are in high demand because it is the main water supply for much of the
west, southwest and Mexico. Around 75% of the runoff for these rivers in the basin
comes from melting snowpack (Cayan, 1996). This makes the region a sensitive,
snowmelt-dominated region.
The Colorado River is one of the most regulated in the world. This is because
it supplies water resources, flood control, and hydropower to many different states,
and even another country (Christensen, 2004). One of the main reasons the river is
so regulated is because of the high demand of the water. Most of the rivers
resources are already allocated to different states and Mexico by means of
regulation and treaties. Any reduction in stream flow will lead to a failure to meet
mandated allocations among the river (Barnett, et al. 2008). It is predicted that by
2050 the maximum spring flow will come about a month earlier in the year. As of
right now, there is not enough reservoir storage to hold the earlier released water
(Barnett, et al. 2008). This means that most of that early water will not be able to be
captured, and will run into the ocean. Current demands for water will not be able to
be met in future climate conditions for many areas in this basin.
Alps
Another area of high sensitivity is in the Alp Mountains in Europe. The main
river these mountains drain into is the Rhine River. This basin is a combined
snowmelt and rain dominated regime (Barnett, et al. 2008). This, in large part, is
because of the topography of the basin. It is more clearly divided between two
sections, the upper and the lower. The upper is more mountainous and the lower
section has more hills and plains (Viviroli, et al. 2004). During the summer, the
lower section of the basin relies heavily on the snowmelt from the Alps for its water
resources. During the winter months, it relies on precipitation, which for the lower
section is rain. With warmer temperatures the Rhine River Basin will become more
of a rain-dominated regime (Barnett, et al. 2008). This changes how the hydrological
cycle impacts this area. Like the western United States, there are major implications
of losing the snowmelt. This can clearly be seen in the lower streamflow during the
summer months (Viviroli, et al. 2004). This has many different effects including the
loss of water resources for domestic, industrial and agricultural uses. Another effect
is the loss of energy from hydropower. A third effect is a decrease in level of flood
protection. The lower stream flow also impacts ships and transport, because the
base flow in this river is a lot smaller then it would have been. There is also a loss of
revenue due to shortened ski season (Barnett, et al. 2008).
The Alps and their basin are a snowmelt-dominated regime. Warmer
temperatures affect their water resources, as well as their economy. The hydrologic
cycle plays a key role in many aspects of the region and it is important to
understand in order to better manage their water resources.
Himalayas
One of the most populated regions in the world is also a snow-dominated,
low reservoir area. Over half of the world’s population lives with in the Himalayan
region (Barnett, et al. 2008). This basin relies on glacier melt for water in the
summer. Almost 2/3 of the water supply during the summer for the Ganges River
comes from the Himalayas (Barnett, et al. 2008). However, unlike other snowmeltdominated basins, this region also experiences monsoons (Messerli, et al. 2004).
Although the monsoons provide some water flow, their main source of water during
the summer months comes from glacier melt. It is well documented that the regions
glaciers are retreating (Barnett, et al. 2008). Due to the nature of a glacier, it will
take time for the effects of the retreating glaciers to hit the region. However, once
the glacier is gone, it is gone. Unlike snowpack, which is annual, glaciers are decadal.
The temperature change of a single year would not affect the glaciers, but climate
change for a decade has huge effects. Since the region relies so heavily on glacier
melt for water resources during the summer months, planning for the future should
be initiated soon to help mitigate the effects of global warming. What is also
interesting to note is five different countries all live in this basin (Messerli, et al.
2004). These countries have to work together carefully when it comes to allocating
water resources. The scarcer the water becomes the more likely tension and
dispute could be created between the counties.
Andes
The last region of significant impact from climate change on the areas water
resources is the Andes Mountains. This mountain range runs all along South
America, residing in seven countries. It is the longest north-south mountain range
in the world (Bradley, et al. 2006). Leaving the area that it affects to be very large.
Specifically for the Central Andes, which include Chile and Argentina, most of the
precipitation falls in the form of snow during the winter months. Agriculture is
extremely important in most of these countries and it relies on the snowmelt from
the Andes Mountain to water the crops. The Andes snowmelt is also the main water
resource in the area, especially when precipitation is low in the summer months
(Corripio et al. 2007). The region surrounding the Andes holds an extremely
diverse group of people. From wealth, to extreme poverty, modern world to
indigenous tribes, there is a large population in the Andes basin as well as a very
diverse one. Because of that, it makes managing water resources an already difficult
task, without water supplies dwindling (Boelens, 2005). However, as shown
throughout the rest of the world, there is no denying the glaciers are melting at a
rapid rate here as well. In Peru, 25% of the glacier-covered region has disappeared
in the past three decades. At these current rates, many of these glaciers may
disappear altogether in the next few decades (Barnett, et al. 2008). This region, like
the Himalayas, relies on the glacier melt for their summer water resource. Without
the glaciers, they will be impacted by water scarcity as well. And again, once the
glaciers are gone, they are gone, and so is their water resource for the summer
months.
Economy
Many of these mountain ranges inspire people to travel to them. A lot of
these countries that these mountains are located in rely on the tourism they receive
as a form of income. Besides the sites, the mountains provide for activities that
attract the tourism.
One of the main sources of attracted is the ski resort. This is heavily reflected
in the Alps. For many areas, winter tourism is the main source of income (Elasser, et
al. 2002). Winter tourism relies on the mountain snowpack. There must be
sufficient and reliable snow conditions in order to attract people during the ski
season. The western United States sees this as well, especially in states like
Colorado or Utah. Many cities, like Park City, Utah, or Aspen, Colorado, rely on their
winter tourism of their ski resorts as their main source of income for their economy
(Bales, et al. 2006). Snowpack has been decreasing world wide, which in turn
decreases the ski resorts ability to bring in skiiers. With climate change, only the ski
resorts in the higher altitudes will be able to stay open. Ski resorts at lower
altitudes will have to shut down due to lack of snow (Elasser, et al. 2002).
It is not just the ski resort that is affected, however, but the hotels and
restaurants too. Businesses in the city rely on the ski resort to attract people during
the winter months and bring in customers.
Nature also attracts tourism to these mountains. In Glacier National Park,
many people visit year round for the sites and seeing the glaciers. It is estimated
that by 2030 most of the glaciers in the park will be gone (Hall, et al. 2003). Not
only is the area losing a large part of its ecological and hydrologic cycle, but it will
also lose many of its visitors and customers. Without that pull of tourism, many
cities will feel the heat of climate change on their economy as well.
Conclusions
Fresh water is one of the most important resources on earth. There is not an
abundant amount of fresh water and the amount that is available is dependent on
the hydrologic cycle. There are many influences of the hydrologic cycle.
Temperature is the most important factor of the hydrologic cycle in snowmeltdominated regions. With climate change and increasing temperatures, the
hydrologic cycle, especially in these mountainous areas, will be affected. Areas of
mid-to-high elevation will see temperature increases over time. Snowpack will be
highly susceptible to these temperature increases. This in turn changes the
hydrologic flow in these basins. This induces many effects, including, lower
streamflow during summer months, loss of hydropower, loss of water resources for
domestic, industrial and agricultural use, and loss of tourism. Warmer
temperatures also change the snowpack’s ability to act as a natural reservoir. It
changes the timing of the snowmelt, which produces a water storage problem for
these areas. It is important for snowmelt-dominated regions to understand the
hydrologic cycle, especially the specific hydrologic cycle for their area. This will
help areas manage their water supply now and for the future.
Warmer temperatures have significant effects on snow-dominated areas and
their basins. The outcome of this is shown all over the world, in both snowpack and
glacier regions. The conclusions are the same; with warmer temperatures these
areas will be heavily affected for their water resources. In the coming future, these
areas need to look at how to better adapt with the change, and continue to manage
their water supply.
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