Improvement of the SPHY Model Glacier Module and its Application in the Tamakoshi River Basin, Nepal
Abstract
Snow and ice reserves are an important source of water for several regions around the globe, especially for the people living in the river basins in the Himalayan region. More than 1 billion people depend on the water resources from the Indus, Ganges, Brahmaputra, Yangtze, and Yellow Rivers. The upstream snow and ice reserves are exposed to the effects of climate change, making long-term water availability in this region more challenging. Increased temperatures result in reduced glacier and snow covered areas due to the increased melting of snow and ice as well as reduced accumulation of snow. To study these snow and glacier melting and accumulation processes, it is crucial to have model concepts available that describe these processes accurately without the need of data demanding energy-balance approaches. For this reason we have improved and validated the glacier module in the Spatial Processes in HYdrology (SPHY) v2.0 model. Within the current version of the SPHY model (v2.0), glaciers are not mass-conserving; i.e. precipitation falling onto the glacier surface as either rain or snow is not accounted for. The current version of SPHY schematizes glaciers as fixed entities melting with a rate depending on temperature and a degree-day-factor. A coarser model grid resolution is often required to be computation efficient in case of larger modeling areas. In this case substantial errors in the estimation of melt from snow and glaciers can be made because of the assumption of the same air temperature for the entire grid cell, which in reality differs for the various glaciers located at different altitudes within the grid cell. Within the improved glacier module for SPHY each model grid cell can contain one or more unique glaciers, being either debris covered or debris free. Each unique combination of model grid cell ID and glacier ID leads to an elevation difference, enabling accurate temperature estimates per glacier in each model grid cell. This makes it possible to calculate snow melt and accumulation, and melt from glaciers more accurately, and make the glaciers in SPHY mass-conserving. As part of a climate change impact study the improved glacier module in SPHY has been tested for the Tamakoshi River Basin in Nepal.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFM.H54A..05T
- Keywords:
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- 1839 Hydrologic scaling;
- HYDROLOGYDE: 1847 Modeling;
- HYDROLOGYDE: 1873 Uncertainty assessment;
- HYDROLOGYDE: 1879 Watershed;
- HYDROLOGY