14 l Glaciers of the Himalayas
Implications of Glacial Change Glacier melt has important implications for the economic sectors that glacier-fed rivers support, particularly in regions where glacier runoff is integral to multiple human activities, such as farming, energy production, supply and quality of water, and tourism. The scale of potential changes facing downstream communities is immense. As noted, the seasonally predictable flow regimes of glacier-fed rivers provide water for hydropower, human consumption, irrigation for agriculture, and tourism. The expected shifts of the hydrologic regime due to glacier and snow melt will have a marked effect on these ecosystem services, with significant economic ramifications (Milner et al. 2017). In the short term, increased water availability is likely to result from continued glacier melt processes. In the long term, however, water resources may decline as glaciers disappear. These future decreases in glacier melt runoff could lead to competition for water resources and worsen water scarcity in the region. Heightened water scarcity would have negative potential consequences for the many environmental, social, and economic sectors that depend on water from the HKHK region. Accelerated glacier melting in the face of climate change is also expected to exacerbate various water-induced natural hazards, such as glacial lake outburst floods (GLOFs) and general flooding, with subsequent impacts on people and assets at risk. Glacial melt contributes to disasters, such as flash floods, landslides, soil erosion, and GLOFs, which occur when glaciers melt and water collects behind a glacier’s terminal moraine (a natural dam of rubble and ice). As these lakes grow and water pressure builds, the moraine can burst, threatening downstream communities and infrastructure. GLOFs have a negative impact on human settlements, infrastructure, hydropower, tourism, agriculture, and other sectors. Roughly 20 glacial lakes in Nepal are currently considered GLOF risks (World Bank 2015). Veh et al. (2018) have identified 19 previously unreported GLOFs in an area covering 57 percent of the HKHK, raising the total count of known GLOFs by 172 percent, based on inventories featuring 11 GLOFs in the region since 1989. Recent research has pointed to an average annual frequency of 1.3 GLOFs since 1980, a figure that has not increased despite the rise in the number of glacial lakes (Veh et al. 2018). Damages from GLOF events are significant. ICIMOD (2011) estimates the damages from potential GLOFs for three major glacier lakes in Nepal as ranging from US$2.2 billion to US$8.98 billion when hydropower project proposals at the lakes are considered in addition to other damages. Another study in Nepal (Shrestha and Aryal 2010) estimates the total value of properties exposed to potential GLOFs at between US$159 million and US$197 million. Glacier melt might worsen the risks of flooding in South Asia. Although direct links between glacier melt and the increased number and severity of flooding events need more investigation, it is highly probable that glacier melt will worsen flood risk through GLOFs or rapidly rising water levels from avalanches of ice and short-term heavy rainfall in the monsoon season. Rapid population growth in the region has increased the exposure to flood risk.
