Natural hazards versus climate change and their potential impacts in the dry, northern Himalayas: focus on the upper Kali Gandaki (Mustang District, Nepal)

In the Himalayas, the consequences of climate change are a fairly debated issue, mainly questioning the availability of water resources to the lowland population. North of the monsoon Himalayas, a semi-arid, continental climate prevails and settlements rely economically mostly on irrigated crops, high altitude rangelands, trade and tourism. The upper Kali Gandaki (Mustang) is situated in this area, with sharp contrasts between valley bottoms (\3,000 m) and high, glaciated peaks (up to [8,000 m). The impacts of climate change may appear in different ways. Gullying is common, and might increase with greater climate variability. Increased ground instabilities (earthflows and occasional debris flows) affecting extensive shale/marly substrates are also expected, linked to changes in snow cover and seasonality. Similarly, the combination of higher snowfall and rapid melting may favour the occurrence of flash floods. The possibility of glacial outburst floods is less probable because of the present limited glaciation. Eventually, permafrost melting may induce rock avalanches down the steepest cliffs and might impact the adjacent valley floors. Collectively, these hazards will affect irrigation canals and fields, new infrastructures and the associated growing settlements. Water availability in the near future is more difficult to predict; however, any change in the amount and nature of precipitation may affect groundwater reserves, hence spring discharge and runoff, with consequences for agricultural products. Eventually, the overall potential increase in natural hazards may jeopardize the development of small markets and the good connection of these upper valleys to the main urban centres of Nepal, a country with a very low economic and social capacity to adjust.