Comparing Source Waters And Flowpaths For Two Glacierized Basins In The Eastern Himalaya's
Abstract
There have been increased efforts to improve our understanding of the dynamics of Asia's cryosphere; yet there are unresolved questions about glacier melt dynamics and flowpaths to river discharge. Here we present a data set of water chemistry along an elevational gradient from the Langtang Valley, Nepal and the Chamkar river basin, Bhutan, to explore how source waters and flow paths might vary in these two glacierized catchments in the Eastern Himalaya's. In both catchments, the O18 values showed a similar pattern of depleted values from glacier outflow of about -16 parts per mil and becoming progressively enriched down-gradient. In contrast, geochemical tracers showed very different patterns for the two basins. For the Langtang basin, the highest concentrations of calcium and sulfate were in glacier outflow and then decreased down gradient. For the Chamkar basin of central Bhutan, concentrations of these geochemical tracers were two orders of magnitude lower in glacier ice, snow and glacier outflow when compared to the Langtang basin, then became more enriched down gradient. A two component mixing model using isotopic data show that for both basins "new" water dominates at higher elevations and decreases down-gradient. A similar model using geochemical tracers indicates more reacted water in glacier outflow for the Langtang basin and decreases down-gradient, while in contrast the Chamkar basin shows little reacted water in glacier outflow and then increasing down-gradient. More sophisticated hydrologic modeling using end-member mixing analysis shows that for both basins groundwater contributions to river discharge increase down-gradient, making a sizeable contribution at elevations of 3,000 m and lower. These results suggest that flowpaths in two glacierized basins of the eastern Himalaya's differ widely. However, in both basins, groundwater is an important source of water to river discharge.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFM.C14B..07W
- Keywords:
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- 0720 Glaciers;
- CRYOSPHEREDE: 0762 Mass balance 0764 Energy balance;
- CRYOSPHEREDE: 0776 Glaciology;
- CRYOSPHEREDE: 0798 Modeling;
- CRYOSPHERE