The structure and function of stream ecosystems in urbanizing alpine watersheds are being changed by human activity by the global effects of climate change and the local effects of nutrients loading by wastewater treatment practices. Snowmelt driven streamflow drives seasonal stream ecosystem cycling and is one of the fastest changing aspects of the hydrological cycle in response to climate change. Headwater streams integrate chemical outputs of adjacent terrestrial ecosystems, and typically nutrient-limited high elevation watersheds are sensitive to increases in nutrients from changes in land use. Dissolved organic matter (DOM) composition in streams reflect an aggregation of transport from uplands and biogeochemical processing: thus, patterns in its character over space and time may inform understanding of the controls on trajectories of stream ecosystems rooted in both hydrological and biological changes. We explored the potential for DOM composition- to represent hydroecological processing regimes in two stream reaches of an urbanizing, alpine headwater stream over hourly, seasonal, and interannual scales in Montana, USA. Using excitation emission matrix fluorescence spectroscopy and parallel factor (PARAFAC) analysis, DOM composition was analyzed in samples collected from upstream and downstream of a highly developed area. We expected the contribution of locally derived DOM during the algal growing season to be controlled largely by stream biomass production, which is influenced by snowmelt flow, time of day, and nutrient loading. PARAFAC analysis five components describing various DOM composition and chemical character of the watershed. Terrestrial DOM was observed continuously, describing a dominant hydrological connection to the soils and groundwaters of upgradient watersheds. Seasonal variation in DOM character was not evident using an overall PARAFAC modeling approach but was evident in more narrow modeling efforts. Understanding the drivers of hydroecological regimes of DOM in an urbanizing alpine headwater stream provides an opportunity to understand the emerging pressures on aquatic ecosystems typically expected to be highly nutrient limited.