Towards better runoff simulation in the Pamir Mountains

<p>Central Asia is a climate change hot spot, facing an unprecedented juxtaposition of regional climate- and water-related issues. Meltwater from the Pamir Mountains plays a crucial role in Central Asia's hydrological cycle, yet there is a little detailed investigation on their response to climate change. Increasing water demand and the assumed ongoing transition from a snow-glacier runoff regime to a volatile rainfall regime in a changing climate demands for a better understanding of the processes governing surface flow in this region. Glacial-hydrological models are key tools for understanding the hydrological response to climate change, informing the planning of possible responses and adaptation. However, modeling is challenging here due to the lack of proper calibration and validation data. Most of the modeling studies in Pamir regions calibrated the model with runoff data only, which is fairly simple but potentially hides internal inconsistencies due to the complexity of feedback mechanisms that govern melt and runoff generation. Further, factors such as model forcing and/or data errors also contribute to simulation uncertainties. There is a clear need for a more detailed investigation of the regional hydrological processes, with systematic calibration and validation methods that allow more robust parameter constraints. This work employed a conceptual distributed hydrological model (SPHY) and tended to unravel the hydrological cycle in a representative catchment in the central Pamir, the Gunt River basin. We tested the usefulness of several state-of-the-art remote sensing, regional climate model, and reanalysis precipitation and temperature data sets in a hydrological application. We found none of them can be equally good in reproducing all targeted hydrological and cryospheric variables (runoff, snow cover fraction, and glacier mass balance). The aims of this study are hence (1) to develop a set of precipitation and temperature correction factors that could improve the model performance, (2) to develop a systematic calibration strategy that could guarantee internal consistency in the simulation of the single hydrological components, and (3) to test whether the corrected forcing data and model calibration strategy can be upscaled to other basins in the Parmir Mountains.</p>