Seasonal snowcover occurs in about 25% of the Earth’s land surface, at high latitudes and high altitudes. The storage of precipitation in snowpack and glacier, and the subsequent melting, substantially impact the water cycle. Recent climate warming and changes in atmospheric circulation patterns have resulted in reductions in the duration of the snow cover season, the amount of water stored in the snowpack, as well as a widespread trend toward earlier spring melt and enhanced glacier melting. Environmental isotopes have a potential to provide an innovative assessment of critical linkages between the discharge from snow and ice systems and rivers/aquifers. The CRP is aimed at assembling isotopic evidence for water derived from snowpack, glaciers, and permafrost, and at isotope-supported estimation of transit times of meltwater through snow and ice layers, residence times in the subsurface and travel times to rivers, lakes and water supply and water energy facilities. Applicability of the results will be identified across catchment scales and with emphasis on their extrapolation under changed climate conditions.