Using Hydrochemistry Data To Constrain The Role Of Snow And Ice Meltwater In The Hydrology Of Langtang Valley, Nepal
Wilson, Alana M. 1 ; Williams, Mark W. 2 ; Racoviteanu, Adina 3 ; Pellicciotti, Francesca 4 ; Juszak, Inge 5 ; Kayastha, Rijan B. 6
1 Department of Geography and Institute of Arctic and Alpine Research, University of ֱ Boulder
2 Department of Geography and Institute of Arctic and Alpine Research, University of ֱ Boulder
3 Laboratoire de Glaciologie et Géophysique de l’Environnement (LGGE), France
4 Swiss Federal Institute of Technology (ETH) Zürich, Switzerland
5 University of Zürich (UZH), Switzerland
6 Kathmandu University, Nepal
Mountains play an invaluable role in regulating hydrologic resources that downstream communities depend on. As our climate changes, it is essential to evaluate the vulnerability of the high-elevation water cycle. An improved understanding of where the water in our rivers comes from is required before we can anticipate changes and devise adaptation measures. In the context of climate change, hydrograph separation methods may provide ways to determine how much streamflow comes from snow and glacier melt versus groundwater and direct precipitation in poorly sampled glacierized catchments in the Himalaya. Understanding hydrograph separation in high-elevation catchments provides insight into how the timing and volume of discharge may change over time.
This work , part of the USAID funded Contribution to High Asia Runoff from Ice and Snow (CHARIS) project, uses geochemical and isotopic data from surface water and precipitation samples collected in the Langtang Valley of Nepal to estimate contributions of meltwater to discharge. Results presented include a comparison of chemistry data from unique end member sources that contribute to streamflow. Additionally a suite of multiple-component (3+) End Member Mixing Analyses (EMMA) using the hydrochemistry data were conducted to test the plausibility of results. Variability in results depending on input suggests that the accuracy of different mixing model methods must be more closely examined before confidently comparing them to results from other types of models. We thus provide an evaluation of different hydrochemistry approaches to hydrograph separation in the Langtang River Basin.