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Abstract. Climate models predict amplified warming at high elevations in low latitudes,making tropical glacierized regions some of the most vulnerable hydrologicalsystems in the world. Observations reveal decreasing streamflow due toretreating glaciers in the Andes, which hold 99% of all tropicalglaciers. However, the timescales over which meltwater contributes tostreamflow and the pathways it takes – surface and subsurface – remainuncertain, hindering our ability to predict how shrinking glaciers willimpact water resources. Two major contributors to this uncertainty are thesparsity of hydrologic measurements in tropical glacierized watersheds andthe complication of hydrograph separation where there is year-round glaciermelt. We address these challenges using a multi-method approach that employsrepeat hydrochemical mixing model analysis, hydroclimatic time seriesanalysis, and integrated watershed modeling. Each of these approachesinterrogates distinct timescale relationships among meltwater, groundwater,and stream discharge. Our results challenge the commonly held conceptualmodel that glaciers buffer discharge variability. Instead, in a subhumidwatershed on Volcán Chimborazo, Ecuador, glacier melt drives nearly allthe variability in discharge (Pearson correlation coefficient of 0.89 insimulations), with glaciers contributing a broad range of 20%–60%or wider of discharge, mostly (86%) through surface runoff on hourlytimescales, but also through infiltration that increases annual groundwatercontributions by nearly 20%. We further found that rainfall may enhanceglacier melt contributions to discharge at timescales that complement glaciermelt production, possibly explaining why minimum discharge occurred at thestudy site during warm but dry El Niño conditions, which typicallyheighten melt in the Andes. Our findings caution against extrapolations fromisolated measurements: stream discharge and glacier melt contributions intropical glacierized systems can change substantially at hourly tointerannual timescales, due to climatic variability and surface to subsurfaceflow processes.