Supraglacial lakes represent an ephemeral storage buffer for runoff and lead to significant, yet short-lived, episodes of ice-flow acceleration by decanting large fluxes of meltwater and energy into the ice sheet's hydrological system. Here, a field-validated methodology for calculating lake volume is used to quantify storage and drainage across Russell Glacier catchment, west Greenland, from 2002 onwards. Using 502 optical satellite images, water volume at ~200 seasonally occurring lakes was derived from a depth-reflectance relationship, independently calibrated and field-validated against lake bathymetry. Inland expansion of lakes is strongly correlated with air temperature: during the record melt years of 2010 and 2012, lakes formed and drained earlier, attaining their maximum volume 38 and 20 days before the 11 yr mean, as well as occupying a greater area and forming at higher elevations (>1800 m) than previously. Although lakes occupy only 2% of the catchment surface area, they temporarily store up to 13% of the bulk meltwater discharged. Across Russell Glacier, 28% of supraglacial lakes drain rapidly and clustering of such events in space and time suggests a synoptic trigger-mechanism. Furthermore, we find no evidence to support a unifying critical size or depth-dependent drainage threshold hypothesis.