Quantification of different flow components in a high-altitude glacierized catchment (Dudh Koshi, Nepalese Himalaya)

Abstract

Abstract. In a context of climate change and water demand growth, understanding the origin of water flows in the Himalayas is a key issue for assessing the current and future water resources availability and planning the future uses of water in downstream regions. This study estimates the relative contributions of rainfall, glacier and snow melt to the Khumbu River streamflow Hydrological Soil Vegetation Model -Glaciers Dynamics Model). One of the main issues in high elevated and glacierized catchments hydrology is the limited representation of cryospheric processes, which control the evolution of ice and snow, in distributed hydrological models. Here, the impact of different snow and glacier parametrizations was tested by modifying the original DHSVM-GDM snow albedo parametrization, by adding an avalanche module, and by adding a reduction factor for the melt of debris covered glaciers. Results show that this new version of DHSVM improves the simulation of the snow covered 10 area and the glacier mass balances, thus improving the reliability of the overall hydrological simulation. In the presented case study, ice and snow melt contribute each more than 40% to the annual outflow. 69% of the outflow originates from glacierized areas. Our simulations also highlight that winter flows are mainly controlled by the release from the englacial water storage. In general, it is shown that the choice of a given parametrization for the snow and glacier processes has a significant impact on the simulated water balance. The sensitivity of the model to the glaciers inventory was tested, demonstrating that the uncertainty 15 related to the glacierized surface leads to an uncertainty of 20% on the simulated ice melt component.

Evaluation of ERA5-Land and HARv2 Reanalysis Data at High Elevation in the Upper Dudh Koshi Basin (Everest Region, Nepal)

“…As already pointed out by Immerzeel et al (2014) and Steiner and Pellicciotti (2016) in the nearby Langtang Valley, there is a great spatiotemporal variability of temperature lapse rates in Himalayan valleys due to extreme topography and the type of glaciers. Instead of a standard environmental lapse rate, it is strongly recommended to use observed lapse rates usually shallower, at high temporal resolution, that is, hourly time scale for instance (Ragettli et al 2015;Mimeau et al 2019). A standard correction method based on spatially and temporally variable lapse rates should be developed to correct surface temperature reanalysis data for the central Himalayas, accounting for not only the season and the hour of the day (Steiner and Pellicciotti 2016), but also the surface state and the location of the measurement site as a function of topography (leeward vs windward for instance).…”

Components of Himalayan River Flows in a Changing Climate

“…Zhang et al, 2013). These studies have used different cryospheric-hydrological models such as Spatial Processes in Hydrology (SPHY; Lutz et al, 2014Lutz et al, , 2016, TOPKAPI-ETH model (Ragettli et al, 2013(Ragettli et al, , 2016, HBV model (Etter et al, 2017;Jost et al, 2012;Stahl et al, 2008), variable infiltration capacity (VIC) model ( L. Zhang et al, 2013;Zhao et al, 2013), the Distributed Hydrology Vegetation Soil Model (DHSVM; Frans et al, 2015Frans et al, , 2016Mimeau et al, 2019;Naz et al, 2014), and Glacier Evolution Runoff Model (GERM; Huss et al, 2008Huss et al, , 2014). There are a few studies which integrate VIC with a glacier model (Ren et al, 2018;Zhang et al, 2013Zhang et al, , 2020Zhao et al, 2013).…”

“…Zhang et al, 2016) including studies focused on Himalayan region (Azam et al, 2019;Immerzeel et al, 2010Lutz et al, 2014Lutz et al, , 2016Rees & Collins, 2006;Shea et al, 2015). Earlier studies have focused on quantifying contributions from glacier melt (Alford & Armstrong, 2010;Racoviteanu et al, 2013a) and other components namely rainfall, snowmelt and baseflow (Brown et al, 2014;Kayastha et al, 2020;Mimeau et al, 2019) to the streamflow in mountainous regions around the world including the Himalayas (Azam et al, 2019;Immerzeel et al, , 2010Lutz et al, 2014;S. Nepal et al, 2014;Racoviteanu et al, 2013b;Savéan et al, 2015;Singh & Jain, 2002;L.…”

Dispositifs techniques de la micro-hydroélectricité et reconfiguration d’un territoire touristique de haute montagne (région de l’Everest, Népal)

“…C'est donc uniquement l'eau des petits affluents qui permet de faire fonctionner les microcentrales pour fournir l'électricité à la population. Ces torrents sont alimentés principalement par les précipitations de mousson et, pour les plus élevés en altitude, par la fonte de la neige et des glaciers (Mimeau et al, 2018).…”

“…La période d'étiage a lieu en fin d'hiver et au début du printemps (de novembre à mai) alors que les besoins sont les plus importants (froid, fréquentation touristique importante au printemps). Les glaciers régulent en partie le déficit en eau des torrents qu'ils alimentent(Mimeau et al, 2018). Malgré tout, les microcentrales parviennent rarement à atteindre la moitié de leur puissance installée : Tok Tok, 40 kW pour 70 installés ; Thade Koshi 40 kW pour 100 installés ou encore Chuserma, 20 kW pour 35 installés.…”