The rapid retreat of tropical glaciers in the Cordillera Blanca, Peru, results in significant changes to the quality and quantity of the streamflow below. Debris-covered glaciers are a common feature in this region but have previously only been studied in terms of their geomorphology and surface characteristics. Short term studies have used hydrochemical mixing models to estimate contributions of melting glaciers to down valley streams. The progressive impact that these glaciers have on streamflow and water chemistry as climate change continues to force glacier loss has yet to be examined. Here we analyze a 16-year dataset (2004-19) of water samples collected from glacierized tributaries of the Santa River draining the Cordillera Blanca, Peru to evaluate inter-annual to decadal differences in hydrochemistry in the outflows below debris-covered glaciers and debris-free glaciers. This unique dataset consists of annual dry season samples from 48 sites within 20 tributaries with different amounts of glacier coverage that provide the isotopic and ionic composition of the water, allowing for analyses of patterns within catchments and comparisons between them over time. Within the Llanganuco catchment, the Kinzl glacier tongue descending from Peru’s highest summit of Huascaran is heavily debris covered (4350-5200 m). Samples directly from the Kinzl effluent stream show the most negative (δ18O = -16.79‰) and variable isotope values (δ18O difference = 3.84‰) compared to less glacierized points within the watershed. In contrast, the Broggi drainage displays the least negative (δ18O = -14.10‰) and variable isotope values (δ18O difference = 2.80‰). Finally, to gain a regional perspective we use the synoptic samples throughout the Callejon de Huaylas watershed to provide a comparison to previous estimates of specific discharge from glacier melt.