Moisture Sources and Pathways Determine Stable Isotope Signature of Himalayan Waters in Nepal


Contact
Hanno.Meyer [ at ] awi.de

Abstract

The Himalayan mountain range produces one of the steepest and largest rainfall gradients on Earth, with >3 m/yr rainfall difference over a ∼100 km distance. The Indian Summer Monsoon (ISM) contributes more than 80% to the annual precipitation budget of the central Himalayas. The remaining 20% falls mainly during pre-ISM season. Understanding the seasonal cycle and the transfer pathways of moisture from precipitation to the rivers is crucial for constraining water availability in a warming climate. However, the partitioning of moisture into the different storage systems such as snow, glacier, and groundwater and their relative contribution to river discharge throughout the year remains under-constrained. Here, we present novel field data from the Kali Gandaki, a trans-Himalayan river, and use 4-year time series of river and rain water stable isotope composition (δ18O and δ2H values) as well as river discharge, satellite Global Precipitation Measurement amounts, and moisture source trajectories to constrain hydrological variability. We find that rainfall before the onset of the ISM is isotopically distinct and that ISM rain and groundwater have similar isotopic values. Our study lays the groundwork for using isotopic measurements to track changes in precipitation sources during the pre-ISM to ISM transition in this key region of orographic precipitation. Specifically, we highlight the role of pre-ISM precipitation, derived from the Gangetic plain, to define the seasonal river isotopic variability across the central Himalayas. Lastly, isotopic values across the catchment document the importance of a large well-mixed groundwater reservoir supplying river discharge, especially during the non-ISM season.



Item Type
Article
Authors
Divisions
Primary Division
Programs
Primary Topic
Publication Status
Published online
Eprint ID
58386
DOI 10.1029/2022av000735

Cite as
Hassenruck‐Gudipati, H. J. , Andermann, C. , Dee, S. , Brunello, C. F. , Baidya, K. P. , Sachse, D. , Meyer, H. and Hovius, N. (2023): Moisture Sources and Pathways Determine Stable Isotope Signature of Himalayan Waters in Nepal , AGU Advances, 4 (1) . doi: 10.1029/2022av000735


Download
[thumbnail of AGU Advances - 2023 - Hassenruck‐Gudipati - Moisture Sources and Pathways Determine Stable Isotope Signature of Himalayan.pdf]
Preview
PDF
AGU Advances - 2023 - Hassenruck‐Gudipati - Moisture Sources and Pathways Determine Stable Isotope Signature of Himalayan.pdf

Download (4MB) | Preview

Share
Add to AnyAdd to TwitterAdd to FacebookAdd to LinkedinAdd to PinterestAdd to Email


Citation


Actions
Edit Item Edit Item