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The complex terrain, high seasonal variability, complexity in precipitation patterns and cold region hydrology at Budhi-Gandaki catchment in central Himalaya, Nepal, presents a challenge for hydrological modeling. Regional or local forcing data, especially with high spatial resolution is preferred over coarser global dataset. However, such data is not always available. The Budhi-Gandaki catchment is subject to significant hydropower development, so accurate discharge simulation is important. Shyft is a novel hydrologic modeling software for streamflow forecasting targeted for use in hydropower production environments and research (Burkhart et al, 2021). It allows easy manipulation with configurations, which is a great tool in decision-making processes in the power production chain. The new functionality of Shyft.hydrology allows capturing of detailed terrain topography using triangular irregular networks (tin) and “on the fly” slope and aspect correction of radiation forcing. We compare discharge simulations using two different forcing datasets: WFDEI global dataset (0.5o x 0.5o) and HI-AWARE regional dataset (5x5 km precipitation and temperature) in both a grid and tin-based configurations. Simulated discharge is compared to observed discharge for ten-year period (2000-2010) using two performance measures, Nash- Sutcliffe efficiency (NSE) and Kling-Gupta efficiency (KGE). We show that the regional dataset combined with a tin configuration performs better than using a rectangular grid resolution, both in terms of NSE and KGE. Furthermore, correcting radiation for slope and aspect at each cell improves the resultant NSE and KGE even more. However, for the global dataset a configuration based on tin performs worse than grid, which is partly attributed to the complexity of the precipitation distribution over the catchment area. One WFDEI grid cell covers the whole catchment, so it is only represented by one precipitation value, which does not allow the interpolation routines in the Shyft.hydrology to separate between windward and leeward areas. However, for less complex terrain and precipitation patterns, like in the Marsyangdi catchment, studied previously (Bhattarai et all, 2020), good results obtained even with the coarse resolution WFDEI dataset. Here introducing a tin configurations improved agreement between simulated and observed discharge as compared to using a rectangular grid. We conclude on the advantages of using a tin-based configurations for water planning in hydropower production in the region. This work contributes to LATICE (Land Atmosphere Interactions in Cold Environments) project at the University of Oslo
Keywords: Central Himalaya; Budhi-Gandaki; Hi-AWARE; Shyft; TIN; Discharge simulation;
References
1. Burkhart, J. F., Matt, F. N., Helset, S., Sultan Abdella, Y., Skavhaug, O., and Silantyeva, O.: Shyft v4.8: a framework for uncertainty assessment and distributed hydrologic modeling for operational hydrology, Geosci. Model Dev., 14, 821–842, https://doi.org/10.5194/gmd-14-821-2021, 2021.
2. Bhattarai, B. C., Silantyeva, O., Teweldebrhan, A. T., Helset, S., Skavhaug, O., and Burkhart, J. F.: Impact of Catchment Discretization and Imputed Radiation on Model Response: A Case Study from Central Himalayan Catchment, Water, 12, 2020.