The Indus basin, located in the Himalaya-Karakoram (HK) region, encompasses a substantial glacierized area, with glaciers of varying scales that play a pivotal role in the hydrological regimes of the major river system. Accelerated glacier mass loss due to anthropogenic climate change poses profound risks to water security, particularly in regions that rely on glacier-fed runoff. While previous studies have primarily focused on regional-scale glacier dynamics, small glaciers (<2 km²)—which comprise ~30% of the glacierized area and 90% of the number of glaciers in Indus basin—remain underrepresented in terms of data coverage and model representation, despite their critical contributions to runoff. This study aims to differentiate the contributions of small and large glaciers to glacier runoff and explore their respective sensitivities to climate change impacts. Using the Global Glacier Evolution Model (GloGEM), we simulate the evolution of all glaciers within the Indus headwaters from 1980 to 2100 under multiple climate scenarios at daily resolution. To enhance the accuracy of our projections, we integrate calibration data from geodetic glacier mass balance and daily snow cover fractions, enabling a more detailed representation of seasonal mass balance processes. Furthermore, spatio-temporal dynamics of supraglacial debris are considered for improved representation of melt and glacier retreat. We analyze the spatial and temporal variability of glacier volume change, the timing of peak water, and the different sensitivities of small and large glaciers to climate change impacts. Our study highlights the critical role of small glaciers, especially in catchments with limited glacier cover, in the hydrological cycle. We stress the need for focused research on small glaciers to better understand their response to climate change and make accurate projections about near to mid-term water availability at local- to regional-scale.