In mountain regions and downstream communities, the challenges of ‘too much and too little water’ are among the primary concerns resulting from climate change (Chettri et al., 2008; Schild, 2008; Eriksson et al., 2009; Sharma et al., 2010; Bajracharia et al., 2010; Rasul, 2011; ICIMOD, 2009). The following findings illustrate the impacts of climate change on people and their environment across the region.
IMPACTS ON THE ENVIRONMENT AND WATER RESOURCES
Over the last 100 years, warming in the Himalayas has been much greater than the global average of 0.74°C (IPCC, 2007; Du et al., 2004). The particular sensitivity of the Himalayas to climate change raises concerns about its role as a major supplier of water to the Asian region. Himalayan glaciers and rivers contribute a high percentage of the water resources for Asia’s main watercourses and basins. The amount and distribution of water in the region has a profound effect on the overall health of many South Asian industries, economies, agricultural production, food security and livelihoods.
As well, the dependence of Asia’s countries on mountain water supplies is even more complex because the average rainfall in the region is so varied and unequal. It ranges from extremely low amounts (<100 mm) in the Kunlun Shan of China to the highest average annual rainfall on earth of more than 12,000 mm in Cherapunjee, India.
For example, the rivers of Nepal contribute to about 40% of the average annual water flow in the Ganges Basin, which is home to 500 million people or about 10% of the total human population of the region. More importantly, these rivers contribute about 70% of the water flow in the dry season (Alford, 1992) and therefore have significant impacts on the bio-physical environments, biodiversity and people.
In China, the Yangtze River supplies water to industry, agriculture, and 500 million domestic consumers. In 2006, the river experienced the flow in its lowest upper reaches since
the 1920s. Upstream dryland expansion, melting glaciers, and aggravated sediment deposits affect downstream flood discharge capacity (Wang et al. 2005) and present risks to the world’s largest hydroelectric installation, the Three Gorges Dam, and its downstream populations.
The importance of runoff originating from snowmelt and glacial melt is also relevant to irrigation use. The Indus Irrigation Scheme in Pakistan depends on runoff originating from snowmelt and glacial melt from the eastern Hindu Kush, Karakoram, and western Himalaya for 50% or more of its water (Winiger et al. 2005). This affects the lives of many people and their livelihoods.
The impact of climate change in the Himalayan region will also lead to more unpredictability of natural disasters. Not only are natural hazards becoming more likely to happen, they are also increasingly destructive and fatal. According to the United Nations International Strategy for Disaster Reduction (UNISDR), seven of the top ten natural disasters in 2008, quantified by the number of deaths, occurred in countries such as Afghanistan, China, India and Myanmar (UNISDR, 2007). In 2007, disasters in Bangladesh, China, India and Pakistan accounted for 99% of the total deaths in disasters worldwide (82% in 2007) (UNISDR, 2007).
TOO MUCH AND TOO LITTLE WATER
Climate change results in increased occurrences of natural disasters and the Himalaya is particularly affected by water related-disasters, often floods. The intensity and duration of such disasters is highly variable and generally exacerbates