Freshwater from the mountains is vital for the region’s economy and for sustaining the livelihoods of a fast-growing population. The largest Asian rivers (e.g., Yangtze, Mekong, Ganges, Indus and Brahmaputra) originate from the surrounding glacierized and snow-capped mountain ranges, which act as “water towers” through transient storage and release of water previously stored as snow or ice,1. The most vulnerable water towers on Earth are located in High Mountain Asia (HMA) and are highly prone to climate change2. HMA extreme topography and contrasted climate is dominated by the influence of two major circulation systems (Mid-latitude westerlies and South Asian monsoon). Consequently, the contribution of glaciers to runoff varies regionally, from 19% in the Dudh Koshi catchment, which is a major tributary of the Ganges (east), up to 81% in the Hunza catchment that drains into the Indus1 (west). The complexity in the land surface atmosphere interactions resulting from these circulation systems hampers our capacity to understand and simulate correctly the meteorological variables. In particular, high mountain (e.g. > 4 000 m a.s.l.) precipitation patterns are poorly understood and existing gridded precipitation products perform poorly3. This leads to large uncertainty in hydrological modelling and quantification of natural water availability in one of the most densely populated areas of the world. In such context, the main objective of this LMI is to assess the spatio-temporal variability of high-elevation precipitation in the Himalayas, with a focus on one region influenced by the Asian monsoon (the Everest region, Nepal), in order to better quantify the impacts of climate and glacier changes on water resources at regional scale. This objective is recognized as a key gap in knowledge in
the Special IPCC Report on the Ocean and Cryosphere in a changing Climate (Chap. 2, p.174) and directly in line with the main scientific challenge in mountain hydrology identified in the recent document “L’hydrologie à l’IRD, p17” High impact studies surveyed the recent changes of HMA glaciers 4, and modelled their future evolution under a changing climate5. However, the link between glaciers, snow and downstream river runoff is still poorly understood because precipitation datasets do not capture the precipitation amount and variability in high-elevation areas3. The need to understand the current spatial and temporal precipitation variabilities is a major challenge to provide a solid basis against which to evaluate the current global and regional circulation model biases, in order to anticipate the local future glacio-hydrological changes and to secure water availability and uses. It is now increasingly understood that the effects of global change, driving a general temperature increase, will be felt also through changes in the hydrological cycle. The risks and uncertainties over the impact on water resources are potentially high in any South Asian countries.
The part of the Service d’Observation GLACIOCLIM (the GLACIers, an Observatory of the CLIMate; https://glacioclim.osug.fr/) dedicated to the Himalayas has been monitoring high elevation glacierized basins in Nepal (Everest region) with local partners for 13 years6. Since 2010 streamflow and meteorological data are collected continuously in the high Dudh-Koshi basin (http://www.papredata.org/, doi: 10.23708/000521). This existing network, rare and unique in HMA, produced the longest series of continuous glacier mass balances and runoff data in Nepal. This observation network, together with the experience shared and gained by the partners of this IJL team thanks to the scientific network developed in the JEAI “HIMALICE” during 3 years, offers the perfect frame and the right opportunity to better understand the spatio-temporal variability of precipitations in the Everest region, as well as their link with the glacier evolution and the high elevation basin hydrology.
This is precisely the aim of this IJL which is the continuity of the JEAI, gathers meteorologists specialized in precipitation assessment (D. Aryal, D. Shrestha), glaciologists (P. Wagnon, C. Vincent, T. Gurung, A. Khadka), hydrologists (S. Nepal, M. Esteves, S. Marahatta, D. Koirala), remote sensing specialists (Y. Arnaud, F. Brun, JP. Dedieu)), and climate modellers (M. Ménégoz). This IJL will be based in Kathmandu (Nepal) and hosted in TU, where a Master programme in Hydrology and Meteorology has been running for 3 decades. A specialized glacio-hydrology course under aforementioned master program has been strengthened with the support of ICIMOD, a well-established regional learning and knowledge sharing centre of the Hindu Kush Himalayas serving eight countries including India and Nepal (http://www.icimod.org/).
To achieve the goals of WATER-HIMAL, the following stages are required:
– Promoting the use of the existing glacio-meteo-hydrological observation network and insuring data dissemination. Combined glacio-meteo-hydrological observations suitable for high elevation glacierized basins are required for the above-mentioned objectives. In terms of glaciological observations, the detailed observational network funded and designed by the GLACIOCLIM Observatory, following WMO (World Meteorological Organisation) and WGMS (World Glacier Monitoring Service; https://wgms.ch/) standards, is operational, in the Everest region. Mera Glacier monitored since 2007 is a worldwide benchmark glacier for the Himalayas. In terms of meteo-hydrological observations, continuous streamflow discharges and meteorological observations are also available in the same catchment (high Dudh-Koshi). The glacio-hydro-meteorological monitoring as well as data dissemination are therefore ensured by GLACIOCLIM, but following a JEAI HIMALICE (2017-2019) between IRD, TU and ICIMOD, this IJL will help to keep on (i) strengthening
this French-Nepalese partnership, and (ii) improving the capacity building.
– Assessing the spatio-temporal variability of precipitation at high elevation in the Himalayas with a focus in the Everest region, in order to better quantify the impacts of climate and glacier changes on water resources at regional scale. To address this objective, an integrated and combined approach is needed, including (i) an analysis of in-situ measurements collected in the field sites described above (WP1 of WATER-HIMAL, resp.: P. Wagnon), (ii) a comparison with available gridded/re-analysed precipitation products such as remote sensing products for precipitation magnitude or snow cover (WP2, resp.: D. Aryal, D. Shrestha), (iii) an assessment of snow accumulation over glaciers by inverting glacier mass balance models (WP3, resp.: F. Brun), (iv) an application of climate models with a focus on the Himalayan region (WP4, resp.: M. Ménégoz), and (v) a distributed physically based hydro-glaciological modelling of studied basins to evaluate the influence of climate and glacier changes on the sustainability of the hydrological budget (WP5, resp.: M. Esteves and D. Koirala).
An IJL will be the right platform to strengthen the proposed South-North partnership in the field of high elevation glacio-meteo-hydrology. By leverage effect, we expect this LMI to locally raise funds to address the objectives of this project and also to be able to offer a regional expertise in the neighbouring countries. Presently, the monitoring of Mera Glacier is funded by GLACIOCLIM, and ICIMOD locally provides some manpower to support it. Complementary to the GLACIOCLIM support dedicated to Mera Glacier monitoring, the LMI budget is planned to 15 000 €/year mainly for internships, publications/conferences, small equipment, travels and meetings. Most of the LMI funds (90%) will be attributed to Nepal, for capacity building, data analysis and research, and the remaining funds (10%) for regional cooperation and networking (i.e. Bhutan and India).
The objectives of this LMI are related to the sustainable development objectives of the IRD POS (“Science au service du développement durable et humain”). This includes (1) the quantification of the impacts of climate change in High Mountain Asia and consequent impacts on population (in relation with ODD 13), (2) the access to water to everybody, with a coherent water management (ODD 6) and (3) the access to high-level education in developing countries such as Nepal with the aim of educing inequalities between countries (ODD 4). This project falls also into the IRD ambitions relatively to the South-North partnership, with the aim of developing a Master programme in Nepal, closely linked to a specialized centre for “Climate Change and Cryosphere”, dedicated to capacity building on HMA cryosphere,
including a multidisciplinary approach. Such centre is essential in South-East Asia, to develop high-level education and research training in the specific fields of high mountain hydrology, climatology and glaciology. So far, there is no structure or organisation to train locally high level scientists in such field, and IRD could play an important role to fill this gap.

1 A. F. Lutz, W. W. Immerzeel, A. B. Shrestha, M. F. P. Bierkens, Nat. Clim Change. 4, 587–592 (2014).
2 W. W. Immerzeel, et al., Nature, https://doi.org/10.1038/s41586-019-1822-y (2019)
3 E. Palazzi, J. von Hardenberg, A. Provenzale, J. Geophys. Res. Atmospheres. 118, 85–100 (2013).
4 F. Brun, E. Berthier, P. Wagnon, A. Kääb, D. Treichler, Nat. Geosci. 10, 668–673 (2017).
5 P. D. A. Kraaijenbrink, M. F. P. Bierkens, A. F. Lutz, W. W. Immerzeel, Nature. 549, 257–260 (2017).
6 P. Wagnon et al., The Cryosphere, 7, 1769-1786, doi:10.5194/tc-7-1769-2013, 2013 and J. Glaciol, Accepted, 2020

Updated on 18 May 2021