TY  - JOUR
A1  - Voss, Katalyn A.
A1  - Bookhagen, Bodo
A1  - Sachse, Dirk
A1  - Chadwick, Oliver A.
T1  - Variation of deuterium excess in surface waters across a 5000-m elevation gradient in eastern Nepal
JF  - Journal of hydrology
N2  - The strong elevation gradient of the Himalaya allows for investigation of altitude and orographic impacts on surface water delta O-18 and delta D stable isotope values. This study differentiates the time- and altitude-variable contributions of source waters to the Arun River in eastern Nepal. It provides isotope data along a 5000-m gradient collected from tributaries as well as groundwater, snow, and glacial-sourced surface waters and time-series data from April to October 2016. We find nonlinear trends in delta O-18 and delta D lapse rates with high-elevation lapse rates (4000-6000 masl) 5-7 times more negative than low-elevation lapse rates (1000-3000 masl). A distinct seasonal signal in delta O-18 and delta D lapse rates indicates time-variable source-water contributions from glacial and snow meltwater as well as precipitation transitions between the Indian Summer Monsoon and Winter Westerly Disturbances. Deuterium excess correlates with the extent of snowpack and tracks melt events during the Indian Summer Monsoon season. Our analysis identifies the influence of snow and glacial melt waters on river composition during low-flow conditions before the monsoon (April/May 2016) followed by a 5-week transition to the Indian Summer Monsoon-sourced rainfall around mid-June 2016. In the post-monsoon season, we find continued influence from glacial melt waters as well as ISM-sourced groundwater.
KW  - stable isotopes
KW  - Himalaya
KW  - glacier
KW  - snow
KW  - precipitation
KW  - seasonality
Y1  - 2020
U6  - https://doi.org/10.1016/j.jhydrol.2020.124802
SN  - 0022-1694
SN  - 1879-2707
VL  - 586
PB  - Elsevier
CY  - Amsterdam
ER  -