Climate change is driving the decline of the global mountain cryosphere. In the past 35 years, North American glaciers have experienced significant mass loss, coinciding with increasingly variable precipitation patterns and an overall decrease in average seasonal snowpack across the western United States. Subsurface ice features, such as rock glaciers—structures composed of a rock-ice matrix insulated by rock debris—are expected to persist in mountain environments even as surface glaciers recede. Meltwater sources are among the most crucial factors influencing the biogeochemical and physical processes in headwater streams. Surface and rock glaciers play a vital role in important ecological processes by maintaining streamflow throughout the melt season, regulating temperatures, supplying essential nutrients (nitrogen, phosphorus, and carbon), and releasing trace elements into aquatic ecosystems. Further, these streams are the source of 75% of the drinking water in the western United States and serve as important habitat for sensitive mountain species. However, meltwater from glaciers can also contain harmful trace elements that may occur naturally in bedrock or from land use practices (e.g., mining). Our research aims to understand how meltwater sources, including seasonal snow, surface glaciers, and rock glaciers, influence physical and biogeochemical processes in mountain streams. In the summer of 2024, we surveyed mountain streams along a latitudinal gradient in the western U.S. from Glacier National Park (MT) to the Teton Range (WY) and the Wasatch (UT). We sampled 18 streams fed by varying meltwater sources and visited each three times during the summer (early-, mid-, and late-season) to capture intra-seasonal variations. During each visit, we collected water samples for analysis of key nutrients (nitrogen, phosphorus, and carbon), major ions, and trace elements and measured physical site conditions. Our results will inform conservation efforts for sensitive aquatic species and management strategies (i.e., downstream water quality treatment and flow management) to mitigate the impacts of changing meltwater sources.