1 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
2 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).
3 Figure 1 is from J Hansen s study on Global surface temperature change. Above shows the annual and 5- year temperature mean from 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
4 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
5 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 " 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
6 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,
7 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).
8 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.
9 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
10 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).
11 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
12 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 snowdominated 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
13 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
14 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
15 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
16 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
17 (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
18 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.
19 References Bales, R.C., et al Mountain Hydrology of the western United States. Water Resour. Res.,42. Bandyopadhyay, Jayanta "Water Management in the Ganges-Brahmaputra Basin: Emerging Challenges for the 21st Century." International Journal Of Water Resources Development 11, no. 4: Barnett, Tim, et al Effects of Climate Change on Water Resources in the West: Introduction and Overview. Climate Change. Volume 62. Numbers Barnett Tim, et al Potential impacts of a warming climate on water availability in snow-dominated regions. Nature Barnett Tim, et al Human-Induced Changes in the Hydrology of the Western United States. Science Boelens, R. and Zwarteveen, M Prices and Politics in Andean Water Reforms. Development and Change, 36: Bradley, Raymond S., et al Threats to Water Supplies in the Tropical Andes. Science. New Series, Vol No Cayan, Daniel R., 1996 Interannual Climate Variability and Snowpack in the Western United States. J. Climate, 9, Christensen, Niklas S The Effects of Climate Change on the Hydrology and Water Resources of the Colorado River Basin. Climatic Change. Volume 62. Numbers Clow, David W "Changes in the Timing of Snowmelt and Streamflow in Colorado: A Response to Recent Warming." Journal Of Climate 23, no. 9: Corripio, J, et al Modeling climate-change on mountain glaciers and water resources in the Central Dry Andes. Darkening Peaks: Glacier. Elsasser, Hans, et al Climate change as a threat to tourism in the Alps. Climate Research. Vol Eos Rethinking Water Scarcity: The Role of Storage. Eos, Transactions, American Geophysical Union. Vol 90. No 28.
20 Hall, Myrna, et al Modeled Climate-Induced Glacier Change in Glacier National Park, BioScience. Vol. 53. No Hansen, J. et al Global surface temperature change. Rev. Geophys. 48. Messerli, Bruno, et al Mountains of the World: Vulnerable Water Towers for the 21 st Century. The Royal Colloquium: Mountain Areas: A Global Resource. Number Pachauri, R.K, et al Contribution of Working Groups I, II and III to the Fourth Assesment Report of the Intergovernmental Panel on Climate Change. International Panel on Climate Change. Pederson, Gregory T., et al "Climatic Controls on the Snowmelt Hydrology of the Northern Rocky Mountains." Journal Of Climate 24, no. 6: United States Geological Survey National Water Information Systems. United States Geological Survey. Viviroli, Daniel, et al The hydrological significance of mountains: from regional to global scale. Hydrology and Earth System Sciences. 8(6) Wtzel, Robert Limnology: Lake and River Ecosystems. Elsevier. Third Edition.