This research will elucidate geochemical and biogeochemical processes that are important at the watershed scale in alpine basins. It will examine these processes using a multidisciplinary approach that combines stable and radiogenic isotopic tracers, plot level experiments, process-level modeling, and field research to constrain the modeling results. New isotopic tools will be used in combination with field measurements of water quality and quantity to separate the relative contributions of atmospheric and soil-derived sources of nitrate in streamwaters, increase our understanding of the biogeochemical reactions controlling alkalinity, and provide insights into the dynamics of sulfur deposition. A key objective is the development of a robust model for solute transport built on fundamental principles to predict the fate of a variety of chemical constituents at many sites and under a variety of conditions. The relevant geochemical, biogeochemical and hydrologic processes are interconnected at the watershed scale and therefore must be studied together. The algorithms used for this ph ysically-based mathematical model provide an integrated approach to modeling the hydrology and biogeochemistry of seasonally snow-covered alpine basins with model development and field work inextricably linked. This research will contribute to a better fundamental understanding of the biogeochemical and geochemical processes, which can be used in responding to anthropogenic perturbations. The multidisciplinary research team has cooperative support from the National Biological Service, U.S. Geological Survey, the National Park Service, and the Long-Term Ecological Research Program. The two study areas are Niwot Ridge/Green Lakes Valley and Lock Vale Watershed, which lie on the east slope of the Colorado Front Range.
