Mountainous regions are vital source areas of groundwater. Hydrologic processes in groundwater source regions are particularly sensitive to climate change due to their high altitude, existence of glaciers and permafrost, and highly heterogeneous geology. While observational technology and hydrologic data for processes above ground are rapidly advancing in recent years, it is vital that more attention is paid to understanding groundwater response to the dynamic changes in order to better evaluate groundwater resource sustainability and future availability. In this session, we present a broad area of groundwater processes in source regions. Topics include: hydrogeologic characterization, infiltration/evapotranspiration processes, impact of glaciers and permafrost on groundwater, tracing groundwater using isotopes or heat, geochemical processes and protecting groundwater quality, interaction of groundwater with surface water, and impact on ecoenvironment.