Contribution of High Mountain Asia glacier changes to river basin hydrology from GRACE and model output products.
Abstract
The High Mountain Asia (HMA) glaciers play a critical role in the water cycle of Asia's main river basins. Quantifying the partitioning of the water balance in these basins is a major challenge due to the complexity of the physical processes operating within the watersheds, coupled with the inherent difficulty of accessing those areas to collect in situ measurements. The magnitude of the precipitation, and the contribution of the glacier and snow melt to the upper and lower basin runoff are large unknowns. We use time series of time-variable gravity from the Gravity Recovery and Climate Experiment (GRACE) mission to document glacier changes in the HMA from 2002 to present and design optimized mascon configuration to evaluate the glacier contribution to the hydrological budget of the Indus, Amu Darya, Ganges and Brahmaputra river basins. We estimate the mean summer runoff in each basin by subtracting the changes in Total Water Storage (TWS) from GRACE, precipitation (P) minus Evapotranspiration (ET) from ERA-Interim re-analysis, and compare our results with river discharge from the Water Balance Model (WBM). We find an excellent agreement between the two estimates. In the Indus and Amu Darya basins, snow and glacier contributions represent more than 60% of the total summer runoff. In the Ganges and Brahmaputra basins, liquid precipitation dominates, as summer melt of snow and glacier melt only contributes 20% of the total runoff. We also find a good agreement between TWS from GRACE and TWS from GFDL atmospheric model (AM4) coupled to a land surface model (LM4). We discuss the implications of the results in terms of projecting future changes in river discharge. This work is funded by NASA HI MAT Science Team Project.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.C21E1387V
- Keywords:
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- 0720 Glaciers;
- CRYOSPHEREDE: 0758 Remote sensing;
- CRYOSPHEREDE: 0798 Modeling;
- CRYOSPHEREDE: 1863 Snow and ice;
- HYDROLOGY