Natural Hazards Versus Climate Change and Their Potential Impacts
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Natural hazards versus climate change and their potential impacts in the dry, northern Himalayas: focus on the upper Kali Gandaki (Mustang District, Nepal) Monique Fort To cite this version: Monique Fort. Natural hazards versus climate change and their potential impacts in the dry, northern Himalayas: focus on the upper Kali Gandaki (Mustang District, Nepal). EnvironmentalEarth Sciences, 2014, [s.p.]. 10.1007/s12665-014-3087-y. hal-01201550 HAL Id: hal-01201550 https://hal.archives-ouvertes.fr/hal-01201550 Submitted on 22 Sep 2015 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Environ Earth Sci DOI 10.1007/s12665-014-3087-y THEMATIC ISSUE Natural hazards versus climate change and their potential impacts in the dry, northern Himalayas: focus on the upper Kali Gandaki (Mustang District, Nepal) Monique Fort Received: 8 July 2013 / Accepted: 20 January 2014 Ó Springer-Verlag Berlin Heidelberg 2014 Abstract In the Himalayas, the consequences of climate good connection of these upper valleys to the main urban change are a fairly debated issue, mainly questioning the centres of Nepal, a country with a very low economic and availability of water resources to the lowland population. social capacity to adjust. North of the monsoon Himalayas, a semi-arid, continental climate prevails and settlements rely economically mostly Keywords Himalayas of Nepal Á Arid uplands Á Climate on irrigated crops, high altitude rangelands, trade and change Á Natural hazards Á Mustang District 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). Introduction The impacts of climate change may appear in different ways. Gullying is common, and might increase with greater The glaciated peaks of the Tibetan plateau and surrounding climate variability. Increased ground instabilities (earth- mountain ranges, such as the Himalayas, make the entire flows and occasional debris flows) affecting extensive central Asian mountains the water towers of Asia (Messerli shale/marly substrates are also expected, linked to changes and Ives 1997), which supply more than two billion people in snow cover and seasonality. Similarly, the combination living in very large cities or in irrigated areas of adjacent of higher snowfall and rapid melting may favour the lowlands (Immerzeel et al. 2010; Singh et al. 2011; Miller occurrence of flash floods. The possibility of glacial out- et al. 2012). In this context, the decline of glaciers (Dy- burst floods is less probable because of the present limited urgerov and Meier 2005) and its consequences on natural glaciation. Eventually, permafrost melting may induce rock hazards and water resources have become of great concern avalanches down the steepest cliffs and might impact the in recent decades (Mool et al. 2001; Kappenberger 2007; adjacent valley floors. Collectively, these hazards will Bajracharya and Mool 2009; Immerzeel et al. 2010) with a affect irrigation canals and fields, new infrastructures and specific focus on the accelerated retreat of glaciers causing the associated growing settlements. Water availability in moraine-dammed lakes to form, hence posing potential the near future is more difficult to predict; however, any outburst flood hazards (ICIMOD 2011). Glacier recession change in the amount and nature of precipitation may is considered the best evidence of climate warming, despite affect groundwater reserves, hence spring discharge and a few exceptions like in the Karakoram where glacier runoff, with consequences for agricultural products. expansion confined to the highest relief glaciers has been Eventually, the overall potential increase in natural hazards recorded (Hewitt 2005). In fact, climate warming remains a may jeopardize the development of small markets and the fairly debated issue in the Himalayan regions, with its consequences that may have been largely exaggerated, especially on the southern, monsoon side of the Himalayas. M. Fort (&) Several models with different outcomes, depending on the CNRS UMR 8586 PRODIG, Universite´ Paris Diderot, primary data and scaling methods utilized, have been Sorbonne-Paris-Cite´, 5 rue Thomas Mann, 75205 Paris Cedex 13, France applied along the 2,500-km-long Himalayan range and e-mail: [email protected] adjacent areas, and their results suggest a clear trend 123 Environ Earth Sci Fig. 1 The Central Himalayan range of Nepal viewed from the north. River, separating the Annapurna Himal on the left from the The Mustang area lies in the lower, central part of the photo. It is Dhaulagiri Himal on the right (Ó2008 William Bowen) drained by the Kali Gandaki River, a major affluent of the Ganges towards warming, but this still has to be checked with field mass wasting in the arid Himalaya. First, the specificity of data (Immerzeel et al. 2013). the central part of the northern Himalayas, i.e. the Mustang Climate warming seems to be a reality in most parts of area in central Nepal, is presented and then the types of Central Asia (New et al. 2002; Kundzewicz et al. 2014; hazards that may increasingly arise from climate change, Lioubimtseva 2013). Average temperatures in Tibet may and potentially threaten the population and their current have risen by as much as 0.9 °C since the 1980s. Higher efforts to develop infrastructures and new sources of warming rates (0.03–0.07 °C per year) have been observed income, are illustrated (Fig. 1). in the central Himalayas and the whole of the Tibetan Plateau (Singh et al. 2011), and average temperature increases of 0.025 °C per year have been recorded around The study area glaciers in the Dhaulagiri Himal (Shrestha and Aryal 2011). The nature (rainfall, snowfall), amount (\300 mm/ The focus of this contribution is the upper Kali Gandaki a) and seasonality of precipitation have also been consid- valley, which corresponds to the northern Mustang District ered, resulting in more uncertainty about their evolution of Nepal. Located north of the Annapurna (8,091 m) and and hence their impacts (Bookhagen and Burbank 2010; Dhaulagiri (8,172 m) ranges, the area falls on the rain- Thayyen and Gergan 2010; Miller et al. 2012). Neverthe- shadow side and is relatively protected from monsoon less, the latest general circulation models (GCMs) project a influences. In contrast with environmental problems that greater increase in precipitation (Immerzeel et al. 2013). In may arise in the southern ‘‘wet’’ Himalaya (Bahadur 2012), fact, insufficient long-term in situ observations and com- Mustang is quite representative of the Trans-Himalayan plex topographic conditions pose major problems for zone characterized by a semi-arid, continental climate, quantifying the magnitude of climatic trends, mostly due to hence by significant temperature variability amplified by differences in topography and microclimatic regimes elevation contrasts (Fig. 2). There is a marked, northward (Kattel and Yao 2013). Whatever their shortcomings are, declining gradient in precipitation in Marpha (28°450N– all approaches confirm climate warming, a trend which in 83°420E, 2,695 m asl.), annual precipitation is around the driest, unglacierized parts of the northern Himalayas 400 mm decreasing to below 300 mm in Jomosom may have specific impacts, such as a decrease in water (28°470N–83°430E, 2,740 m asl.), then below 160 mm in resources for irrigation and rangelands, upon which the Lo Mantang (29°100N–83°570E, 3,800 m asl.). Inter-annual survival of populations living in these remote places variability is high, for example in Lo Mantang with ‘‘wet’’ depends. years such as 1978 (298 mm) in contrast with very dry This contribution focuses on the impacts that climate years as recorded in 1982 (85 mm). Snow precipitation change might have on natural hazards such as gullying and prevails during wintertime and at an elevation above 123 Environ Earth Sci Fig. 2 a The arid, upper Mustang area, located on the northern, rain- seasonality, influenced by a continental character and elevation; shadow side of the Himalayas: structurally controlled, the Thakkhola- elevation in metres asl., annual mean temperature, and mean annual Mustang graben offers only limited sites for villages, i.e. the Late precipitation are given for each station. Muktinath is in the upper Quaternary terraces overlooking the Kali Gandaki canyon (Ó1978 M. valley of Kagbeni, Jomosom is 10 km south of Kagbeni, Ghami is just Fort); b The upper Kali Gandaki north of Jomosom (Mustang District, on the left of the photo (a). Note that these meteorological data, Nepal) is marked by high relief and violent winds. Note the absence collected from the Department of Hydrology and Meteorology, of continuous vegetal cover and the extensive irrigated fields of Government of Nepal, are only estimations established in selected Kagbeni and Tirigaon (2,800 m, middle ground) (Ó2009 M. Fort); years with reliable records (Diagrams adapted and redrawn from c the precipitation-temperature diagrams reflect a dominant aridity Dobremez 1976; Fort 2000a; Miehe et al. 2002) (stippled area, dry season; grey areas, wet season) and a complex 2,500 m, but exceptional snowfall can occur at any time of severe (Fort 1987; Fort 2000a). The growing season is the year. Spells of summer rainfall are not rare, whereas short and does not allow more than one crop per year characteristic, strong valley winds have a severe desiccat- (buckwheat, wheat, naked barley). Population density is ing effect, reinforced by sharp, topographic contrasts over a low, with fewer than 5 inhabitants/km2.