Evaluating the hydrological regime of the snow-fed and glaciated Hunza basin in the Hindukush Karakorum Himalaya (HKH) region

In the high altitude Hindukush Karakorum Himalaya (HKH) mountainous region, the complex weather and terrain and sparse measurements make the precipitation distribution and hydrological regime significant unknowns. Recent advances in remote-sensing and reanalysis-based global precipitation products and numerical models may provide more insights on the hydro-climatic regimes for such regions. This study examined the precipitation distribution and snow and glacier melt contributions to river flow in the highly glaciated and snow-fed Hunza basin of the Karakorum mountains. The Distance Distribution Dynamics (DDD), a rainfall-runoff model with its temperature index and an energy balance approach for glacial melt, was used. The model was forced with precipitation estimates based on a newly developed and fine resolution (0.1°×0.1°) gridded product of ERA5-Land. The model calibration and validation were performed from 1997–2005 and 2006–2010, respectively. The mean annual precipitation of the Hunza basin was estimated as 947 mm from 1997–2010. The precipitation distribution analysis showed more precipitation at lower elevations than at higher. The simulated snow cover area (SCA) was in good agreement with MODIS satellite-based SCA. The flow analysis indicated that the Hunza’s flow is strongly controlled by glacier melt (44–47 %) followed by snowmelt (31–32 %) and rainfall (22–23 %). The simulations showed that the DDD model has good potential to simulate hydrological processes satisfactorily for data-scarce basins.