(Featured image: Imja Glacier – Broken lake ice at the debris-covered terminal cliff, with scarred inner face of moraine beyond and Baruntse in the background. Photo taken by Michael Hambrey, 2003)
Author: Jieling Liu
Abstract: The article analysed major river runoffs, glacier mass loss, precipitation and surface temperature changes in the Himalaya region. The paper’s quantitative analysis of historical precipitation matched the result run by the climate model CMIP 5. Decreasing precipitation and rising surface temperature as results of climate change have cost the Himalaya region glacier retreats and shrunk river runoffs. The living environment for 40 million local residents has become drier in dry areas and wetter in wet areas. Hot and cold extremes have been putting additional challenges to them. Future projections suggest more radical glacier retreats and increasing precipitation, which can be catastrophic to the local livelihoods. The paper also gave suggestions on future solutions to the intensifying water challenges from financial, political and social perspectives. Both international support and local effort are needed to overcome the current water challenges that the Himalaya region is facing. Possible solutions include financial supports to improve infrastructure, actions to ratify mitigation targets, green energy development and good community practices in water use.
Keywords: Himalaya, water resources, monsoon activities, glacier retreat, climate change
Even with the wide-spread technology and comparatively advanced economy that we have today, around 1.2 billion people still live in areas of physical water scarcity. Water scarcity will be an even greater challenge when the world population reaches 9.7 billion by 2050 (UNDP, 2006 & UNDESA, 2015). Water, as one of the climate system’s principal mediator elements, might react to the climatic changes in the forms of melting glaciers, sea level rise and biodiversity reduction. Melting glaciers are increasing flood risks and reducing water supplies, predominantly threatening populous regions such as the Indian sub-continent and parts of China (Stern, 2006).
The Himalaya region is an excellent regional model for studies to find solutions to the global water challenges under the circumstance of climate change. The high mountain range contains a lot of glaciers, ice and perpetual snow and is therefore referred as the “third pole” (Bahadur, 1993). The extremely high altitude region originates 10 major rivers in Asia that cover a densely populated area. Its powerful summer monsoon is a significant component of the global climate system. Yet the region is one of the least explored geographical zones on the planet.
Melting glaciers and increasing water demand are the two great conflicts challenging the people in this region. The area’s glaciers are retreating at astonishing rates. The particularly fast retreat is observed in Bhutan, Nepal and neighbouring parts of China (UNEP, 2009). The area went through rapid population growth and urbanisation development. From 1901 to 1981, the region’s population tripled from 11 to 33 million; today it supports around 40 million people. Although the combined drainage basin scatters almost three billion people in 18 countries in total (Karan, 1987 & WWF).& Given the region’s population and economic development status, the demand for freshwater will unquestionably grow to meet the increasing energy and water-intensive agriculture need.
The Himalaya’s water reserve changes in the last decades are the central issues to be described in this article. In addition, impacts of climate change are explored with the references of climate model future projections. Finally, the paper discusses potential future solutions from financial, political and social perspectives, addressing both on a more sustainable readjustment of water distribution and on adaptation strategies to extreme climate events.
2. Previous studies
Bahadur (1993) systematically portrayed the Himalayas with focuses on its polar-like environment and monsoon climate, hoping to provoke international interests to monitor the unique high mountain environment. Recent studies on the Himalayas mostly found changes in the monsoon precipitation and glacier retreat due to warming surface temperature. Wang and Ding (2006), Zhou et al. (2008), Hsu et al.(2011) and Wang et al. (2012) observed weakened land monsoon precipitation in the region, especially in the Northern Hemisphere (NH). Shekar et al. (2010) also found declines in seasonal precipitation and the number of snowfall days. In addition, they also observed increases in maximum and minimum temperatures in the western Himalaya.
Through tree-ring reconstructions from the western Himalayas, Yadav et al. (2011) confirmed a 20th-century warming in the Tibetan Plateau, Tianshan Mountains and western High Asia. UNDP marked in its Climate Change Science Compendium 2009 astonishing retreat rates between 10 and 60 metres per year of the Himalayan glaciers. The paper noted that retreat rates of 30 metres per year have become common. Scherler et al. (2011) measured more than 65% of the monsoon-influenced glaciers retreating. In subdued landscapes on the Tibetan Plateau ice is disappearing even faster. Kääb et al. (2012) found regionally averaged thinning rates under debris-mantled ice were similar to those of clean ice, despite insulation by debris covers. Bolch et al. (2012) concurred that most Himalayan glaciers are losing mass at rates similar to glaciers elsewhere and predicted that, continuing shrinkage will enlarge the runoff seasonality, affect irrigation and hydropower and may even alter hazards.
Changes in glacier melt in warmer atmosphere signify changes in river runoffs. Barnett et al. (2005) made notions on the shift of intense seasonal runoff from summer to early spring, hinting the possibility of increasing water stress in the warmer months. Chaulagain (2006) fortified the exacerbating seasonal imbalance of water in Nepal, a monsoon-dominated region where floods and landslides strike during heavy monsoon seasons and droughts during dry seasons. Chen et al. (2007) found the runoff of the Tarim River (Northwest China) exhibited a significant increase during the last 20 years. They did not exclude the possible attribution to global climate change.
3. Research methodology
The paper’s research method is a combination of quantitative analysis of the water resource changes in the Himalaya region and a review of climate model projections. The study tracks down historical data from the Global Runoff Data Centre (GRDC), International Centre for Integrated Mountain Development (ICIMOD) and National Aeronautics and Space Administration (NASA) for the observation of water resource changes. Major river runoffs and glacier retreats are analysed thoroughly to develop a comprehensive Himalayan hydrological portrait.
Then, precursor environmental conditions such as land surface temperature and precipitation trend will be inspected to find climate change impacts on water resources. The examination of climate change impacts is done by evaluating the consistency between the model projections and the quantitative analysis.
4. Geographical condition, climate and water resources of the Himalaya region
80 million years ago, India broke away from the Supercontinent and collided into Asia after 30 million years. The intercontinental smash formed the Himalaya Range and gave rise to the highest mountain on the planet. Today the Himalaya hosts more than 90 peaks that are above 6000 metres between the Tibetan Plateau to the north and the Indian alluvial plains to the south. Nine out of the world’s 10 highest peaks are formed, including the highest Mount Everest with an elevation of 8848 metres. The Himalaya Range is therefore called “the Roof of the World” (Bishop & Chatterjee).
The Himalaya is geographically approximate to the highly energetic tropics. This puts it at the centre of massive interactions between the Indian ocean moisture and the lower surface pressure of the sub-continent, which results in the monsoon. The seasonal phenomenon is responsible for producing the majority of wet season rainfall within the tropics (IPCC 2013). The region is referred as “the third pole” as it stores 50% of all glaciers outside of the polar areas (Bahadur, 1993). The Himalaya’s magnificent heights result in the eternal snow and abundant lower-valley glaciers. They collectively form the sources of 10 major rivers in Asia, including the Yangtze, Mekong and Brahmaputra, ranking the third, fourth and fifth largest by annual volume of discharge respectively (Wohl, 2007). The 10 rivers run through 18 Asian countries and nourish more than 3.2 billion people, 43% of the world’s total.
Figure 1. Map of the Great Himalaya Range
The region generates a variety of local climates ranging from tropical at the foothills to permanent ice and snow at the highest elevations. Due to its location and extreme height, the Himalaya Range is a great barrier between the north and south sides. Cold continental air from the Tibetan Plateau is blocked by the Himalaya from penetrating into India in winter; the southwesterly monsoon winds also lose most of their moisture before tramping over the range northward. This feature brings heavy precipitation (both rain and snow) on the Indian side but arid conditions in Tibet (Bishop & Chatterjee). Together these local climates intervene the global climate and hydrological system.
5. Climate change in the Himalaya region
Major rivers in this region experienced a decrease in the runoff in the last decades. Figure 2 exhibits eight principal river systems – Brahmaputra, Amu Darya, Ganges, Indus, Irrawaddy, Mekong, Yangtze and the Yellow River – and their long-term mean monthly discharges. The data was recorded by local monitoring stations and collected by GRDC crossing a time span of 40 years. Stations that are relatively near the Himalaya Range are chosen in this study to maximise the value of the analysis. Most rivers, e.g., the Yangtze (blue line), Mekong (purple line), Amu Darya (light green line), Yellow River (yellow line) and Brahmaputra River (dark green line) showcased diminishing monthly discharges. The Indus and Irrawaddy River are shown with an increasing runoff trend; however, due to their relatively short monitoring time and the incompletion of the GRDC datasets, Figure 2 is not fit for explaining the runoff evolution of these two rivers.
Source: Figure created by the author based on the data from GRDC
Figure 3. Average yearly change in ice mass during 2003-2010 in the Indian Subcontinent
*Measured by NASA’s Gravity Recovery and Climate Experiment (GRACE) satellites, in centimetres of water. The dots represent glacier locations. Blue represents ice mass loss; red represents ice mass gain. Source: NASA/JPL-Caltech/University of Colorado
Over 54,000 glaciers in the Himalaya Range comprise over 6,000 km3 of ice reserves. They act as important fresh water reservoirs for the region (ICIMOD). In the past decades, glacier receding is becoming another evident phenomenon of the warming climate. Figure 3 presents the average yearly change in ice mass in the Indian Subcontinent between 2003 to 2010. Significant ice mass loss — up to 4 centimetres of water in the glaciers — has occurred in this region, but concentrated mainly in the southern plains. On the contrary, the Tibetan Plateau on the northern side is gaining ice mass. This phenomenon is mainly occurring around the Karakoram Mountain. The southern ice mass loss is mainly caused by groundwater depletion (NASA).
Figure 4. Himalayan precipitation and temperature variability during 1951-2007 Source: ICIMOD
Comparing the monsoon activities in the two time period 1951-1980 and 1981-2007 (see Figure 4), we learned that precipitation also underwent changes in the Himalaya region and is getting polarised. In general, rainfalls concentrate in the south and east side of the Range. No big changes in the average intensity of precipitation. However, there is a great difference in the number of rainy days between the east and west side. Dry areas such as northwestern India is becoming drier, wet areas such as Assam, Meghalaya, Bihar are becoming wetter.
Changes in surface temperature are also observed in this two time period. In average situations, a great difference of up to 40oC differs the north side from the south both in winter and summer. In extreme cases, the minimum temperature in the winter dropped down to -40oC; in the summer, the maximum temperature went above 50oC – a temporary burning environment that caused many deaths. A 3oC anomaly in both lowest and highest temperatures are observed. Rising temperature anomaly occurred mostly in the southern Range and covered a broader area than decreasing temperature anomaly.
Figure 5. Cumulative frequency of GLOFs and flash floods in the HKH region Source: ICIMOD
A series of natural hazards occurred in response to the rising temperature and melting glaciers in the Himalaya region. Many high-altitude glacial lakes are identified to be dangerous. As water and ice debris in these lakes accumulate, the moraine dams can be broken easily. Glacial lake outburst floods (GLOFs) and flash floods during the heavy monsoon season are common and disastrous to the Himalaya region. Multi-decadal observations have proven the uprising of these hazards (see Figure 5). From 1950 to 2000, the number of flash floods occurred increased by six times; GLOFs occurred four times more frequently. The increasing trend of such natural hazards has also become more radical.
6. Climate model projections on water resource changes
Increasing moisture flux from ocean to land is a key atmospheric change. Climate models incorporate it to project changes in the monsoon activities. In the CMIP5 multi-model projections, the global monsoon area, global monsoon total precipitation and precipitation intensity in the future are expected to increase by the end of the 21st century, no matter which RCP scenarios (Hsu et al., 2013; Kitoh et al., 2013 & IPCC, 2013).
On the regional scale, land monsoon domains of East Asian summer (EAS) and Southern Asia (SAS) are expected to encounter the same fate. Figure 5 presents time series of observed and model-simulated summer precipitation anomalies relative to the present-day average. The decreased precipitation in the last five decades matches with the long-term mean monthly discharges of major rivers that are shown previously in the quantitative analysis in Chapter 5. Future precipitation trends for the two land monsoon areas are projected to rise. In the RCP 2.6 scenario, precipitation increase is projected to be smooth and to peak around mid 21st century. The higher the global ambient CO2 concentration is, the more radical the precipitation increase is projected to be.
Glacial melt has been observed worldwide and is projected to continue at an increasing speed in the future. According to Lutz and Immerzeel’s analysis, in the worst case scenario – the RCP 8.5 wet and warm environment, glaciers in the Mekong and Salween Basins are projected to lose nearly 70% by 2050. Even in a reasonable scenario – the RCP 4.5 wet and cold environment, where radiative forcing will be stabilised in 2100, glaciers in the Indus Basin are going to lose 20% by 2050.
Figure 6. Changes in precipitation indices over the regional land monsoon domains of EAS and SAS based on CMIP5 multi-models Source: IPCC, 2013
7. Possible solutions to the Himalayan water challenge
Previously we discussed the changing climate in the Himalaya region — warming surface temperature, polarised monsoon activities and its reactions — melting glaciers and decreasing river runoffs. The region is projected to gather more water resources in the future, but that is not the problem. Heavy precipitation and melting glaciers may cause hazards like floods and landslides, which are the real threats to local livelihoods. Pasture and agriculture activities in this region are water-sensitive. The region’s basic mountain infrastructure expose people in great danger once these hazards strike.
International financial support, or development aid, is necessary to help the region fortify the infrastructure both to preserve water and to protect them from severe hazards. In addition, mitigation also relies on international effort to curb carbon emission. The Paris Agreement target of 2oC, the ingenious carbon trade scheme and the thriving renewable energy development are just some of the examples that, global endeavour can make great differences on the fate of the Himalaya’s water resources, as ice and glaciers are extremely sensitive to the global temperature changes.
Local governments in the Himalaya region can explore future solutions through developing hydropower. If intended to construct hydropower stations, the dams will also be better equipped for water conservation and more effective for flood discharge. Good adaptation also requires a scientific monitoring system that would provide better environmental assessment for territorial planning and cope with disasters. Communities in the same social environment can empower themselves by exchanging good experiences in the sustainable use of water, sharing knowledge on disaster prevention and make decisions that are consequential to better water supplies to the whole community.
8. Conclusion and future works
As the results of climate change, rising surface temperature and decreasing precipitation have cost the Himalaya region glacier retreat and river runoff reduction. The paper’s quantitative analysis of historical precipitation matches the result run by the climate model CMIP 5. The living environment for 40 million local residents has become drier in dry areas and wetter in wet areas. Hot and cold extremes have been putting additional challenges to them. The further consequence is: all these climatic changes and their influences to the region’s water resources are impacting the combined drainage basin that almost three billion people scatter.
Both international support and local effort are needed to overcome the current water challenge that the Himalaya region is facing. Possible solutions include financial supports to improve infrastructure, actions to ratify GHG mitigation targets, green energy development and good community practices in water use.
Although, given the Himalaya Range’s origin from tectonic plate collision and is still an active orogen, its climatic activities are extremely dynamic and complex. In other words, current climate change evidence might not be comprehensive to explain the changes of the Himalayan water resources. Further studies incorporating geological insights and more recent data are needed, to better understand how climate change may impact the Himalayan water resources and to propose good future solutions to the precious liquid that we rely on for life.
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