The glacier-hydrological model TOPKAPI-ETH was set-up for the Rio Santa catchment at a 100 m resolution for a present period (2008-2018), this allowed the validation of model outputs against a range of data, including field and remotely-sensed glacier mass balance, river runoff, surface albedo and MODIS snow line elevations. The model results were then analysed to investigate the importance of snow and ice melt for runoff both spatially and seasonally. The results revealed the ephemeral nature of the snow cover below 5000 m a.s.l. which results in a highly variable wet season snowpack. The results of this work were published in Nature Communications Earth and Environment.
The TOPKAPI-ETH model was then run for the past period (1987-2018), with the outputs successfully validated against three datasets of historical glacier outlines. The outputs of the past runs were analysed to investigate the spatial and temporal variation in glacier mass balance. This allowed the drivers of glacier mass balance and runoff change to be determined, with a particular focus on the role of El Niño on influencing catchment processes. The model was then run into the future, from 2018-2100. These runs were forced by 12 CMIP5 projections under an RCP 4.5 emissions scenario which had been statistically downscaled to match the WRF climatology. These results were analysed alongside the past run to investigate the ‘peak water’ paradigm within the Rio Santa catchment. To do this the long-term variation in ice and snowmelt contributions to runoff were analysed, not only at the scale of the entire Rio Santa basin, but also at the sub-catchment level, revealing contrasting responses depending upon the sub-catchment glacier cover.
Then the work shifted in scale to the Shallap sub-catchment, where the Tethys-Chloris model was applied. A suite of field data were collected within the Shallap catchment over two field seasons in June 2024 and July 2025, designed to provide input, calibration and validation data for the modelling work.The field work included the installation of soil temperature and moisture sensors, trail cameras for snow monitoring, vegetation data collected within the proglacial forefield, glaciological data of ablation and debris-thickness and drone imagery across the catchment.
The Tethys-Chloris model includes a full energy and mass balance approach to modelling catchment processes allowing a more in-depth assessment of the impact of succession vegetation on catchment runoff. The multi-point set-up of the model was run to allow calibration and initial assessment of the model results. Then, the fully distributed model was run at a 50 m resolution (2015-2019) to give results on the importance of glacier, snow and vegetation processes on the water and energy balance of the catchment. These results allow insights into the relative importance of the cryosphere compared to ecological processes, and provide the basis for an assessment of how these will shift under future conditions.
